OO-1855: add a configurable possibility to prepend the external id of course to their WebDAV folders

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-1069: round of optimizations, escape the & character, async reload the list of courses, groups and shared folders...

OO-1004: encode softly the webdav names for group and resources to preserve as much as characters as possible

OO-1004: encode softly the webdav names for group and resources to preserve as much as characters as possible

OO-470: merged containers are transient with an init method to initialize them after deserialization

OO-157: optimization of WebDAV, reduce the number of DB queries with lazy loading, specific resolve method, lazy loading of quota...