As baggy theme was removed and material is the only remaining theme, we don't need a theme switched anymore.
So:
- move all `*.twig` files from the material theme folder to the root
- remove useless translations
- a big message will be displayed to user using the Baggy theme
- switching from Material to Baggy is no more allowed in config (it'll be forced to material)
- the theme label in the config for Baggy is now _Baggy (DEPRECATED)_
- convert english translation to translate key
- remove baggy template for login (never used since user isn't logged in and it'll use the default theme: material)
- fix tests about text in response (now checking translation key instead of translated text)
- remove all ugly `<div class="hidden">{{ form_rest(form) }}</div>`
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 :))