Redesign protocol instructions

**Is your feature request related to a problem? Please describe.**
The Guacamole protocol was designed for long connection over TCP. `sync` and `nop` instructions intend to pause the connection without breakfast. Nevertheless, during the connection IO, tons of `sync` and `nop` meaningless communication are made between client and server, which slows the server performance. Besides, Occamy involves WebSocket as a default option implicitly keep the connection alive. Therefore the only necessary instructions are control and renderer instructions.

**Describe the solution you'd like**
We would like to propose removing all unnecessary instructions and only kept the control and renderer instructions. This proposal requires large reimplementation of `libguac`, it is unclear
that this level of refactoring involves how many of `cgo` calls, which may slow the server due to Go runtime. An investigation is required absolutely.