Detect RPM specfiles

Currently `scancode-toolkit` can scan packages or any kind of code without targeting metadata like type of package (`for example : RPM`). For any given RPM the `.spec` has most of the `metadata` like `architecture, source RPM, URL etc.,` and it is the most reliable `metadata` for that RPM. So, we need to have a separate scanning scenarios for RPMs. Everytime `scancode` enounters an RPM it should provide `scan results` using these scenarios.