Fix wssshc registration message to send password instead of request_id

- Added send_registration_message() function to websocket library
- Updated wssshc.c to use send_registration_message() instead of send_json_message()
- Registration message now sends: {"type":"register","client_id":"<id>","password":"<password>"}
- Instead of: {"type":"register","client_id":"<id>","request_id":"<password>"}
- Server can now properly authenticate clients with passwords