[eclass] Add KDE Applications support.

For all applications:

- Add SRC_URI support
- Add mirror restriction for prereleases

For KDE 4 based applications:

- Support kde-apps/oxygen-icons
- Automatically block kde-base/${PN}
- Modify add_kdebase_dep to use kde-apps, with a blacklist for packages with no
  applications release

For KDE 5 based applications:

- Introduce add_kdeapps_dep in a similar vein to the other add_kde*_dep functions
Revert "[eclass] Sync kde4-functions with tree"

This reverts commit ff16e62967f4afebe715141599170941c24f706f.

The overlay version is more recent.

Conflicts:
	eclass/kde4-functions.eclass
[eclass] Remove special handling for old versions.