Implement services and clients in rmw interface

[nightduck]

• [ ] rmw_create_client - Makes client
• [ ] rmw_destroy_client - Cleanup from above
• [ ] rmw_send_request - Publish, but for client
• [ ] rmw_take_response - Take, but for client
• [ ] rmw_client_request_publisher_get_actual_qos - Self explanatory
• [ ] rmw_client_response_subscription_get_actual_qos - Self explanatory
• [ ] rmw_create_service - Makes service
• [ ] rmw_destroy_service - Cleanup from above
• [ ] rmw_take_request - Take but for service
• [ ] rmw_send_response - Publish but for service
• [ ] rmw_service_request_subscription_get_actual_qos - Self explanatory
• [ ] rmw_service_response_publisher_get_actual_qos - Self explanatory
• [ ] rmw_service_server_is_available - Returns true until we get networking up
• [ ] rmw_set_log_severity - Logging stuff
• [ ] rmw_get_service_names_and_types
• [ ] rmw_get_service_names_and_types_by_node
• [ ] rmw_get_client_names_and_types_by_node

Unit tests from test_rmw_implementation to pass

• [ ] test_service
• [ ] test_client

[nightduck]

Added dummy holders a67145fe7667d9e8e5f1c7f6a02d73475fdde15b

[nightduck]

Since there's no message reuse, the concept of using message queues doesn't make much sense here. But also I hate networking, so I'm just going to implement them as named pipes for now. In the future, they can support implicit memory copy operations, for convenience, but will serve little performance benefit from it.