GUAC-653: Move terminal code to common location.
GUAC-653: Update namespace in common terminal code.
GUAC-653: Move mouse and key handling into terminal. Move clipboard into terminal.
GUAC-653: Separate terminal API into public/internal/low-level pieces (in spirit).
GUAC-653: Implement render_frame function.
GUAC-653: Remove direct reference to internal terminal pipes.