RFR: Support yaml metadata for actions and rules

* Add: Yaml support for actions and rules meta. Both yaml and yml extensions
are supported.
* Add: yaml, yml and json meta for sample action in fixtures for testing.
Fixed in ccf79a048020f5576c87d9d6faedd4b5058c4436, 76b8a5c26a32df51ee0a5f5ef44afceea7aa8ef9