Remove version 0.8.4 and obsolete 0.9.2 ebuilds

Also remove older versions of ebuilds from dependencies.
Fix minor ebuild issues
Depend on virtual/libusb instead of dev-libs/libusb
Use gentoo mirrors instead of website in SRC_URI
Avoid deprecated eclasses

This means transition from inheriting python or distutils to python-r1
and distutils-r1, as well as from git to git-2.
This in turn required EAPI=5, so all ebuilds were moved to EAPI=5.
Fix KEYWORDS for libsuinput and libg15-gnome15

Mark amd64 and x86 as stable for now.
Add metadata for portage-2.2
Fix use.local.desc
Add gnome15-stable keywords file for >=0.9.6

Update readme accordingly.
Also remove stale -9999 keywords file.
Replace dev-python/imaging with virtual/python-imaging
Use virtual/python-imaging instead of dev-python/imaging

Seems PIL only supports python2, so gentoo is slowly moving away from
it, preferring pillow (a fork of PIL) in most ebuilds.
Gentoo also marks these packages as conflicting, and is removing
dependencies towards dev-python/imaging from existing ebuilds.
Add more packages to gnome15-stable