Follows-up I301f471f86ba2.
For ease of navigation, move Converter subclasses to a group called
"Languages", which for documentation purposes is a subgroup of
"Language". The next commit does the same for Messages* files,
and Language subclasses (done separately for ease of review).
Change-Id: If1cef9aa15f536ebaedd4477ad7453426e7f3b85
Add se-FI, se-NO and se-SE for Finland, Norway and Sweden,
respectively. The fallback languages for each are set to
the country's major official languages.
Bug: T299341
Change-Id: I54959494336e439337f622ae3eebb127883db789
