**Increments Plugin API Version**
Adds functions:
- `obs_websocket_get_api_version()` - Gets the current obs-websocket
plugin API version
- `obs_websocket_call_request()` - Calls an obs-websocket request via
the plugin API
Adds structs:
- `obs_websocket_request_response`
- Implements a WIP ObsWebSocketApi, for obs-websocket-api.h. Events are
finished, but requests are not.
- Some logging improvements
- A bit of code cleanup around the plugin