Add Unit test framework and provide unittests for DB API

testtools and fixtures for performance improvements compared to unittest
Please use test.py as a base for further unittests

Re: DB API testing, only CRUD lease has been tested, CRUD Reservation
and Event shall be tested too. I will provide another review once I'll
finish the Manager Extension for Host Reservation.

Refactoring previous unittests for using the framework
Rebased requirements

Change-Id: Ia9a187c45e40f891c8478fb234dd021cffadbe03