conf: Post-release version bump
meld.build_helpers: Record some installation prefixes (bgo#730322)

On install, we now record the installation prefix in the meld.conf
module, so that we can locate our CSS, icons, etc. in non-standard
prefix build environments. This should also make jhbuild of Meld
actually work.

This method was inspired by gottengeography, and then it got ugly.