Move the functions of OlatRootFile and OlatRootFolder to the Local
implementations to simplify the use of VFS, implements factory methods
in VFSManager, reduce the number of call to meta informations in folder
listing

OO-2541, OO-2536: optimize resolve method of merge source for the standard case, add virtual "finished" folder for finished courses, lazy load quota for the course container

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-291:  enhance the main search function for groups, add search in waiting list, add search of public group, add unit tests

OO-291: first step: move business gourp manager to a business group service, remove dependency to the context...

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