mate-user-share-1.5.1: Version bump + misc updates

Package version bump to 1.5.1
Bump EAPI to 5
Add MATE_PUNT_LA and remove custom punting in src_install
Remove libnotify 0.7.0 patch. Upstream supports it with [1].
Now uses dconf so remove gconf (note this ebuild never had mateconf!)

[1] https://github.com/mate-desktop/mate-user-share/commit/3b15531a8d6f85bf654289deffe67c0893c70857
mate-user-share-1.5.0: Remove old ebuild