Implement PARAM_VALUE handling, add parameter functions, minor UI change

- Added case 22 in mavlink_msg_handler for handling PARAM_VALUE messages
- Converted handle_function_call to async
- Added functions for use in handle_function_call:
  - get_parameter
  - get_all_parameters
  - get_parameter_description
  - set_parameter
  - get_mavlink_message
  - get_available_mavlink_messages
- Made small UI adjustments
- Made small UI adjustments

Author: esatiyev