Fix python-numpy documentation for real

Binary package hint: python-numpy

Bug 664276 was fixed by disabling the matplotlib plugin. This was good because there is now no dependency between main's python-numpy and universe's python-matplotlib. It's bad because the documentation will not include plots that are useful to end users.

After discussion with the <email address hidden> mailing list, I think Colin's original idea is the least worst: create a new source package for Ubuntu only which includes the upstream numpy tarball and builds only the documentation. Then we'd move python-numpy-doc binary package out of the standard (main) numpy source package and move it to the (universe) numpy-doc source package.

Any way we slice it, we're going to diverge from Debian. Unless someone can come up with a better idea, I think this allows us to stay as close as possible while still providing full documentation.

Or, maybe we can keep the main documentation as it is and add a new binary package something like numpy-doc-complete in universe.