setup: better version handling

* Replicates version handling from Flask-Registry. (closes #9)

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
global: uniform file licence headers

* Adds header containing licence information to each source file.

* Amends copyright years for every source file based on its git
  commit log history.

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>