It has to be sure that all parents are visible and accessible as well.
This wasn't achieved sometimes in the current evaluation logic.
Additionally I simplified the learning path access algorithm thank's
the usage of the stored assessment data.

The NodeEvaluation makes it difficult to use a course node in the
learning path access concept. So it is refactored to a minimum extent,
so that it can covering the previous functionality.
As a replacement a new security callback and a new tree node type is
introduced.

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

course element

and the single participant folders