KDE 4.14.1

This is my initial attempt of KDE 4.14.
It is based on https://nixos.org/wiki/How_to_upgrade_KDE and https://github.com/NixOS/nixpkgs/pull/3054 . Some commits are the same except for 4.14.
Currently it all builds, and things seem to work to some degree (only tried running a few programs).

TBD Telepathy update (check the commits in the referenced pull request). I didn't do this in fear of breaking KDE 4.12.
At least on my system, installing kde414 pick up kde-workspace-4.11.6 . That's the reason why i have noticed that line of code.

kde-open --version
Qt: 4.8.6
KDE Development Platform: 4.14.1
KIO Client: 2.0

ls -ld /nix/store/*kde*/| grep workspace

...kde-workspace-4.11.6/
...kde-workspace-4.11.5/
...kde-workspace-4.11.6/
...kde-workspace-4.10.5/
...kde-workspace-4.11.5/
...kde-workspace-4.11.6/