Support returning language array in language files

[ewinslow]

For example, instead of doing:

add_translation('en', array(...));

we simply do

return array(...);

and Elgg should already know which language to put them in based on the file name.

Just a little shortcut for the lazy amongst us, plus it is backwards compatible with the add_translation method.

[ewinslow]

Fixed in [34edcf8bbb383537adc80bdcd4a629af8918b889]