things for a future user preferences management system
Preferences back-end and front-end.

Some new preferences meant to be used by the client arent yet.
room creation page better rendered on mobile
fixed the unconsistent rendering of the Cancel bouton in the room creation page
fixed the cancel behavior in room creation/edition page when cancelling before creating the room
notification
merge master
'settings' icon next to user name to make it clear it's clickable
A preferences now enables the display of message date on hover, on breaks or always
Save button on preferences page is displayed only when there's something to save
Save button on /username page is displayed only when there's something to save
Merge branch 'prefs'
fixed a bug in notify in pages without userprefs