Since password are linked to username it was hard to change username while checking that the password is the good one.
Instead of doing crazy things to achieve that, I act that user won't be able to update username.
Also, username (and email) must be unique, since people logged in using username and can request a new password using email.
This should fix#1149
Re-defined the config / user relation to be OneToOne bidirectionnal.
ConfigType is now a service so I can inject the list of available themes that are also used by LiipThemeBundle
Force sqlite for test
In case of people use a different driver in parameter.yml (yes I do :))
