[entropy.db.skel] fix matching of old style virtuals

When only a subset of the packages in a given key, slot expose
an old style virtual dep string (like virtual/linux-binary-lts),
make sure not to pull in all of them instead.
[Rigo] add "in:exact" command to allow users to match packages, use it for lts kernels

Conflicts:
	rigo/rigo/ui/gtk3/controllers/applications.py