numerix refactor

Following the extended discussion of namespace clashes on the dev and
users list, and some discussions with Todd offlist, I took a new
approach to fix these problems. The central sticking points were

1) pylab should not override built-ins

2) numerix should be faithful to the underlying packages while providing
    a consistent interface to them. Hence numerix would not change
    the names of the functions in mlab

3) pylab imports the numerix symbols, but didn't want to have a
    different policy than numerix.

The resolution to this dilemma was to refactor numerix to preserve the
namespaces. numerix now attempts to mirrors the numarray directory
structure for namespaces (though this is currently incomplete as I
just added enough to satisfy the needs of matplotlib). So you now do

  from matplotlib.numerix.mlab import min, max, mean
  from matplotlib.numerix import arange, array
  from matplotlib.fft import fft

and you'll get the proper symbols from Numeric or numarray depending
on your numerix setting. For convenience I added amin, amax to mlab
and asum to numerix, though the original python incompatible symbols
min, max, sum still reside in their correct numerix locations
unchanged. At some point Todd will pull numerix out as a freestanding
module, I think, which will make for less typing since the
matplotlib prefix can be removed.

The decision for numerix package structure to mirror numarray's seems
like a good one to me, since everyone is still hoping to see Numeric
disappear, and this provides the most natural path. When the great
merging occurs, one can simply globally replace numerix with numarray
and everything will follow.

pylab still imports (almost) all the symbols from numerix,
numerix.mlab, etc, except the ones that clash with python names. In
their stead, pylab imports amin, amax and asym. pylab also tries to
be a good citizen and defines __all__, to avoid problems like the time
module problem described by danny on the user's list.

This is explained in a little more detail in API_CHANGES.

I've tested this a good bit and everything seems to be working. I am
trying to get a release out the door for Joe Cooper to fold into his
enthought build which is going out Monday. I would like to put a
release up this afternoon on the user's list.

Would you kind folks here mind taking this for a test drive and submit
comments, feedback, problems, back to me as soon as possible?

It would also be helpful if you would inspect the __all__ var of pylab
to see if you think its correct. Currently:

  date2num, num2date, drange, epoch2num, num2epoch, mx2num,
  DateFormatter, IndexDateFormatter, DateLocator, RRuleLocator,
  YearLocator, MonthLocator, WeekdayLocator, DayLocator, HourLocator,
  MinuteLocator, SecondLocator, rrule, MO, TU, WE, TH, FR, SA, SU,
  relativedelta, array, zeros, shape, rank, size, fromstring, take,
  put, putmask, reshape, repeat, choose, searchsorted, asum, cumsum,
  product, cumproduct, alltrue, sometrue, allclose, arrayrange,
  arange, asarray, convolve, swapaxes, concatenate, transpose, sort,
  argsort, argmax, argmin, innerproduct, dot, outerproduct, resize,
  indices, fromfunction, diagonal, trace, ravel, nonzero, shape,
  where, compress, clip, zeros, ones, identity, add, logical_or, exp,
  subtract, logical_xor, log, multiply, logical_not, log10, divide,
  maximum, sin, minimum, sinh, conjugate, bitwise_and, sqrt, power,
  bitwise_or, tan, absolute, bitwise_xor, tanh, negative, ceil,
  greater, fabs, greater_equal, floor, less, arccos, arctan2,
  less_equal, arcsin, fmod, equal, arctan, hypot, not_equal, cos,
  around, logical_and, cosh, arccosh, arcsinh, arctanh,
  cross_correlate, pi, ArrayType, matrixmultiply, rand, randn, eye,
  tri, diag, fliplr, flipud, rot90, tril, triu, ptp, mean, msort,
  median, std, cumsum, prod, cumprod, trapz, diff, cov, corrcoef,
  squeeze, kaiser, blackman, bartlett, hanning, hamming, sinc, eig,
  svd, angle, roots, amin, amax, linspace, window_hanning,
  window_none, conv, detrend, detrend_mean, detrend_none,
  detrend_linear, corrcoef, polyfit, polyval, vander, entropy,
  normpdf, levypdf, find, trapz, prepca, fix, rem, norm, orth, rank,
  sqrtm, prctile, center_matrix, meshgrid, rk4, exp_safe, amap,
  sum_flat, mean_flat, rms_flat, l1norm, l2norm, norm, frange,
  diagonal_matrix, base_repr, binary_repr, log2, ispower2,
  bivariate_normal, inverse, eigenvectors, fft, Int8, UInt8, Int16,
  UInt16, Int32, UInt32, Float32, Float64, Complex32, Complex64,
  Float, Int, Complex, TickHelper, Formatter, FixedFormatter,
  NullFormatter, FuncFormatter, FormatStrFormatter, ScalarFormatter,
  LogFormatter, LogFormatterExponent, LogFormatterMathtext, Locator,
  IndexLocator, FixedLocator, NullLocator, LinearLocator, LogLocator,
  AutoLocator, MultipleLocator, plotting, colormaps,
  get_current_fig_manager, connect, disconnect, get_plot_commands,
  raise_msg_to_str, axis, axes, delaxes, clim, close, clf, colorbar,
  draw, figtext, figimage, figlegend, figure, gca, gcf, gci, get,
  hold, ishold, isinteractive, imread, load, rc, rcdefaults, save,
  savefig, set, subplot, title, xlabel, ylabel, xlim, ylim, xticks,
  rgrids, thetagrids, yticks, polar, over, ioff, ion, axhline,
  axhspan, axvline, axvspan, bar, barh, cohere, contour, csd,
  errorbar, fill, hist, hlines, imshow, loglog, pcolor,
  pcolor_classic, pie, plot, plot_date, psd, scatter, scatter_classic,
  semilogx, semilogy, specgram, spy, spy2, stem, vlines, cla, grid,
  legend, table, text, autumn, bone, cool, copper, flag, gray, hot,
  hsv, jet, pink, prism, spring, summer, winter, Line2D, Polygon,
  Rectangle, Circle, Text, cm, get_cmap, normalize, show