mate-desktop-1.5.8.ebuild: Ebuild cleanup

Remove commented src_prepare, patches applied upstream.
Remove old gtk3 comment, handled by package.use.mask.
mate-file-manager: Remove old ebuild versions
mate-image-viewer: update Manifest
mate-menus-1.5.0: Bump EAPI + update DEPEND

Bump EAPI to version 5
* Buildin functions die by default in EAPI >= 4.

Bump DEP on mate-common to version 1.5
mate-panel-1.5.6: update DEPEND + remove old ebuilds

DEP on mate-menus-1.5 and mate-common-1.5
Remove old version of the ebuilds.
mate-session-manager-1.5.2: Update deps + remove old ebuilds

Remove old ebuild version.
Upate DEP to mate-common-1.5
mate-settings-daemon: remove old ebuild versions
caja-dropbox-0.7.1: remove dep on lib{mate}notify + misc cleanup

Nowhere int the source does it include any lib{mate}notify.
* remove DEP on libmatenotify

Use MATE_LA_PUNT instead of custom punting.
* Remove custom punting in src_install