OO-3489, OO-3492, OO-3493, OO-3494, OO-3496, OO-3497: infrastructure to export user data, export  portraits, notes, personal folder, calendars, subscriptions, delete calendars after usser deletion

OO-1068 OO-1113 more bootstrapify of forum, refactor redundant avatar image code, add forum attachment preview

OO-887: cache the usernames in UserManager, decouple the AvatarMapper and make it search the username in the cache.

OO-372,OO-96: implements mappers which can be persisted on the database, implements the infrastructure, implements the scorm mapper and the file mapper for iframe to be serializable/deserializable,

--HG--
branch : bps