MuranoPL testing mini-framework

Introduces simple helper layer for testing MuranoPL code.
It provides customized class loader for sample test YAML classes and
fluent syntax to build Object Model and invoke various methods on it.

Also contains basic test that tests both the framework and the very basics of
MuranoPL execution

Change-Id: I3c1dfea4ea29824cb3149b122ce9cf95365d32bc
Implements: blueprint muranopl-testing-framework
Merge "MuranoPL testing mini-framework"