Translation2

* Updated translation branch to current master
* Updated resource handling to ```PlatformUtils::resourcePath()```
* Dropped most of the non-GUI calls that caused lots of merge conflicts
* Windows installer tested, that looks ok now (MXE build is using the host gettext for now)
* Added Czech translations from #614.

TODO:
* [x] Merge the PlatformUtils code with master; wait for #1008 to be merged first due to conflicts
* [x] Make the compiled .mo files available from a development executable ("locale" folder vs. "po" folder)
* [x] Test Linux snapshots
* [x] Test Mac snapshots
* [x] Test Windows snapshots
* [x] Final code review (@kintel)
* [x] Look into when to do .po file generation. Right now it's done at build-time which is a bit confusing (removed from build)