Add support for processing CSAR files and include necessary unit tests.
Note: Since CSAR files used do not already exist on github a temporary
URL has been used. Once the patch merges a follow-on patch will be
submitted to update the URL to a github URL.
Change-Id: Ibf44be1368ed0144ecf415068b0ca5aea5aa6134
Partially-Implements: blueprint tosca-csar-translation