Roll back unwanted config changes.
Added some tests for the Language helper.
Optimization of languages names translation.

Memoization of the big languages code-to-name array. Sounds like calling
gettext like hell (especially from codeToName() called for each flag
display) brings performance down. Loading time of /sentences/show/1 lowered
from 4.5~5.5 to 2.5~4.0 seconds here.