Authorization Management replaced by a solution without sessions

wrote query to sum up the number of watchlist entries for an exercise id, then wrote the test and merged development into my branch

This needs a lot more work, but at least runs.

Remove search by type. This had to be done because
type was changed to learningResourceType, which is
a free string and no longer an enum.
String search for type could be added in the future.

Disable suggestions for format. This was done because
in the current version format is no longer a list
but a single string. There are problems with that, so
this might change again.

Lots of tests fail.

This reverts commit 72c9a602.

refactored statistics so that they are loaded by the statistics service and then resolved the collections bug