added to the interfaces the features requested by Vlado: label/lastwrite/lastread logs, encryption key and lbp tag for tapes; and encryption flag for pools

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.

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.

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

Some legacy utilities from castor were imported alongside, with some adaptations.