FIX migration down (NOT NULL)
Installed DoctrineFixturesBundle.
Merge branch 'topic/fixture' into topic/user
Created fixture for loading sample User data.
Updated vendors (DoctrineMigrationsBundle, sql-formatter, KnpMenuBundle, swiftmailer, Twig).
Merge branch 'topic/setup' into topic/security
Merge branch 'topic/user' into topic/security

Conflicts:
	composer.lock
Work in progress... (fixing fixture)