config/application.rb: Add Polish locale (pl)
config/application.rb: Add Polish locale (pl)

This activates the Polish translations from #476.

The app should now show in Polish for browsers with "pl"
in a preferred position of their Accept_Language headers.
RefugeRestrooms/refugerestrooms,RefugeRestrooms/refugerestrooms,RefugeRestrooms/refugerestrooms,RefugeRestrooms/refugerestrooms