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.

Change-Id: Id203e62b040ddc2fe67399b2b487eaddca5f564f
Partially-Implements: blueprint repository-reorganization