OO-3016: optimize "Linked with course" in the business group search, reduce the number of relationships to course which are search every time

OO-2975: delete imported calendar after course, group and user deletion, implement a check every 10 runs to remove deprecated imported calendar, append the job to the scheduler

OO-2878: add attachment to the info messsages, add the possibility to send the emails only to owners, coaches or participants and not all of them

OO-2740: remove the email of the person leaving the group from the email to the person gaining access to it (patch S. Clemenz)

OO-2676: simplify html code of calendar event editor and repository info editor, replace synchronized in velocity with a ConcurentHashSet to reduce lock contention, remove double update method for groups...

OO-2479: reduce overhead everywhere, optimized and simplified query to count the participants of a group, bypass reloading the group set of identities, bypass reloading the base group of business group...

OO-1873: replace the listing of booking by a native query optimized for our standard setup, replace the .hbm.xml with annotations, add more fetching overall

OO-1645: propagate the business rules for private event on home calendar and calendar tool of the course

OO-1616: replace the view for the business group lists with several customized queries which load only the needed data

OO-1647: remove auto-subscribe of course calendar, list of course which the user is member of and which have a calendar ( as configuration or as course element)

OO-1615: springuifie mail package, rest package, question pool module... remove unused dependencies...

OO-1559: add sync of coaches by ldap user attributes, refactor the batch sync to handle mix configuration with attributes and group bases at the same time

OO-1511: remove relation to assessment mode if a business group is removed from a course, add unit tests