Move locale.ini to obs-studio base data directory

Being in with the other locale files causes a bit of confusion,
especially since the locale files will all be renamed to have .ini
extensions.
Rename locale extensions from .txt to .ini

Because we're using .ini format, the translation servies spit out files
with .ini extensions, so this makes it so we don't necessarily have to
rename those files from .ini to .txt before merging.