[ticket/12983] Correctly validate sorting options in the UCP

PHPBB3-12983
[ticket/12983] Add functional test for ucp pref module

PHPBB3-12983
[ticket/12983] Do not test invalid values until Symfony 2.4

PHPBB3-12983
Merge pull request #2925 from nickvergessen/ticket/12983

Ticket/12983 UCP preferences, Display posts ordering by: input is not properly validated
Merge branch 'develop-ascraeus' into develop