Merged in murano-common

In attempt to reduce number of Murano repositories to a sane minumum Murano
community decided to merge in murano-common repo to projects dependent on it:
* murano-api
* murano-agent

We hope that we will completely get rid of this code in Juno.

Partially-Implements: blueprint repository-reorganization

Change-Id: Ia18958c937b2c983d84b39a5a7849788ed9df6eb