Added some database-level support for User language preference. Part of #977
Updated UnitTestHelper and ModelFactory to account for language preference. Part of #977
Implemented language preference from API up to UI and some fixes to DB schema to account for it. Login related code still needs to be changed to actually change the site language by reading language preference info from DB. Part of #977
Merge branch 'develop' of gitlab.trommons.org:solas-match into develop