[Linaro-validation] metadata format is now mandatory for test-definition

Hi,

With help of Amit Khare we managed to update metadata on all YAML files in test-definitions.git repository. I added automated check for metadata format and contents. So if any patch has invalid metadata, the sanity check will fail. This change was introduced because the docs are generated automatically basing on the metadata. It doesn't affect any actual testing results.

Best Regards, Milosz Wasilewski