[Localization] Where to put .mo files for sugar?

[Alexander Todorov]

>>>> It should be /usr/share/locale/aa_EE/LC_MESSAGES/, where aa_EE is your
>>>> language code.

I see there that most aa_ee are simply 2 char language abbreviation.
There is a bg for Bulgarian. Should I put my .mo files there and test or 
I create a bg_BG one ?

Another question:
As it seems hard to find out the .mo filenames is there a list of them?
e.g. should it be chat.mo or chat-activity.mo ?

Any quick guide in configuring the default language ?

Thanks,
Alexander.