(cherry picked from commit 6751a8a9)

Conflicts:
	adminstuds.php
	app/classes/Framadate/Utils.php
	creation_sondage.php

(cherry picked from commit e6d171a4)

Conflicts:
	app/classes/Framadate/Utils.php

(cherry picked from commit 16da5370)

Conflicts:
	app/inc/constants.php.template
	app/inc/init.php

Cherry-picked :
        e6d171a4

Conflicts:
	app/classes/Framadate/Utils.php

+ Use this system to migrate from 0.8 to 0.9 (WIP)

admin: Add some logging on important actions (delete poll, clean votes, clean comments, drop column)

+ Simplify call to remove all votes of one poll