#10 assignmentfolder base_view cleanup

[fRiSi]

since baseview of assignmentfolder is visited often by
students that navigate to their assignment sheets this
could be cleaned up.

at the moment all attributes, references to statistic
models and objects that are in the folder (statistics,
assignments) get listed.

proposed solution

name of the folder
all the assignments that are in there (searched with
the catalog to just get the public ones)

maybe responsibilities too (which lecturer is
responsible for which group)