translation files: to remove

Hi mkiol,

I noticed the translation files under translations/ are semi-generated, which adds many files whenever there is a new build, resulting in a "dirty" git status even with small changes.

It artificially adds +28 files to commits whenever the user has to rebuild the app.

What do you think of using qt_add_translation for normal builds, and add a custom update_translations target using qt_create_translation for when translation files actually need updating?