API inconsistency and payload props naming

[RobinTail]

This is actually not a pin, it's a relay index (r1..r8).

OctoRelay/octoprint_octorelay/__init__.py

Lines 84 to 85 in fc54cf0

	UPDATE_COMMAND: [ "pin" ],
	GET_STATUS_COMMAND: [ "pin" ],

It should be renamed.
In order to do this without breaking changes, we should support backward compatibility somehow.

[RobinTail]

get_api_commands lists mandatory parameters, so basically, it should become empty to support backward compatibility

[RobinTail]

There is also a chance to align payload props, having "active", "status", "result" and other inconsistent naming for relay states.

[RobinTail]

Another issue is that some API errors responses have status code 200.
There should be a way to to flask.abort with message.