[basemap] support shapefile in a zip archive

thru data.gov, there are several shapefile archives available, in a zip format.

Do someone believe it worths to support this kind of "distribution" of
shp or we'd like still to have the zip unzip'ed first and the
readshapefile() the resulting file?



Sandro Tosi (aka morph, morpheus, matrixhasu)
My website: http://matrixhasu.altervista.org/
Me at Debian: http://wiki.debian.org/SandroTosi