Specify GUI language in Cmake via CLI

[luzpaz]

Add the possibility to download only certain languages via CLI flag
see Scribus Cmake flag for this

[luzpaz]

The current idea is that if one needs to speed up compile in order to test or simply prefers; they can do it in english only. I can make a brew flag to to pass only english to cmake (just like in the travis.yml file)

-DWANT_GUI_LANG=en_US;