middletier, itself separated in interface, SQLite, objectstore and
shared tests.
Moved all utilities (exceptions, threading...) to a shared utility
directory.
Created a single, shared unit test from all the scattered ones.

Ported the user tests to the new structure.

Used exceptions while moving Vfs to creating its temporary directory using mkdtemp. This allows several Vfs intances to run on the same
system simultaneously.
Updated the model of the abstract unit test so it can instanciate one test environement per unit test. This was needed in the current
unit test for middle tier admin.

Duplicated the SQL middle tier unit tests and turned them into templated tests for re-use with other implementations of middle tier.

License comment is no longer filtered out by doxygen when generating web pages of the individual source files.

Moved previous versions of object store tests in a diffrent directory. They will eventually be removed.