This new "simple" data driver takes serialized partitioning info
that is provided before provisioning from external tool.
It does not make any calculations for that data and expect it to have
all required informations about partitioning.
Other changes:
* added unittest2 to use some of it features
* added requests_mock to mock http requests
* added objects conversion to/from dictionary to make serialization
easier
* added a common "interface" for data drivers
* fixed test for "do_build_image" - now a correct data driver is used
Change-Id: I673cde6f0ead9945919a87cd1cfce7ed09c6e593
Implements: blueprint volume-manager-refactoring
9e22866f3e