Add translations to cmake

[houz]

I started adding translations to the cmake builds.
Attached you will find a diff and two new files that I didn't manage to get into the diff (total bzr noob here).

Currently it will create and install a .mo for every .po file present (not limiting itself to the ones in LINGUAS as the autotools based installs do). That would be easy to add, but since all available .po files are in LINGUAS anyway I wasn't sure if that is a feature that is actually used or just the way the build system was once set up.

It also lacks a make target that updates the .po files from the .pot.

[houz (houz)]

First missing file.

[houz (houz)]

Second missing file.

[Mc (mc...)]

I think i managed to get it working, but it took me hours to find that i needed to add

+include(CMakeScripts/FindGettext.cmake) # custom FindGetText

to the CMakeLists because it was otherwise not used (and the system one was used, leading to the wrong names, and no install...)

[Mc (mc...)]

pushed in r14304