gNumExp almost ready for a release

This is it. After todays' commit, gNumExp's port to goocanvas and gtk+ 2.10 (for printing) is more or less complete, and we have feature parity with the 0.10 release made about one year and a half ago.

So, code-wise the hardest part is done, but I'd like to do some polish first, before the release:

1. Include a copy of goocanvas and pygoocanvas;
2. Don't rely on bonobo-activation to startup numexp-kernel, instead do our own custom activation, using a hardcoded path to the binary discovered during configure state;
3. [Maybe] stop using libgnome*, use only gtk2, libxml2, and gnomevfs.

Even next release won't be 1.0, I'd still like it to be more polished than usual.