Transfer metadata by copy / upload / download of zip files, unify copy
of streams, copy metadata during copy of courses, remove backwards
compatibility mode for import

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

Rearrange the different settings in the same place with a segment view
for all resources. Implement a new flag for resources "bookable" which
indicates the entries with a booking methods. Guests users doesn't have
a right to view courses with booking methods.