Added support for specifying review language during creation.
Added new API interface that returns list of all supported languages.
Updated server tests.
Added language selector on review creation page.
Updated docs.
Fixed supported_languages variable access.
Updated layout of the home page.
Updated messages.pot
Updated messages.pot
Updated margin for "Popular reviews" title on home page.
Merge branch 'review-lang'

Conflicts:
	client/messages.pot