Remove usage of python.eclass

(I got tired of waiting for somebody else to fix these errors, so I decided to finally scratch my own itches ;-) . I hope that this overlay is still active!)

This series of commits has the goal of removing all consumers of the old python.eclass, which has been gone from the main portage tree for a while. Most ebuilds I was able to update to the -r1 eclasses (sans revbump because the ebuilds don't work as-is anyway), but several I decided to remove, either because development has stopped and getting them to build would be too much work for me (libclam and friends, jokosher), or because the sources have become unavailable (xmms2tray), or because they have newer versions in the main portage tree (the rest). In some cases the packages had already been fixed and I only had to remove old versions/revisions.

After these changes, repoman only gives me two hard errors (which I have already fixed in a different branch, which I plan on submitting after this merge request is done).

Some notes:

1. The removal of patchage breaks drobilla further (it also depends on a non-existent version of graphviz), but that package needs to be fixed/updated anyway (or maybe a non-live ebuild could be created instead).
2. Whenever I touched a package, I aimed at getting it repoman clean, so there are several unrelated commits (e.g., fixing metadata.xml, shortening DESCRIPTION).
3. I haven't build tested everything (e.g., some of the non-* packages), but I assume that this needs some review first, anyway, and it would be better for me to test this on my desktop, where I have some of the dependencies installed already (i.e., testing on my laptop would be too slow for my taste).
4. Also, I'm not 100% sure if some packages might need python-single-r1 instead of python-r1.