Introduce track command in 3rd order spg.
With this command the spg is set to track the 'track_x' input but will
still honour all limits (v, a, j, x)

Fix block dependencies

Various small fixes
Add command protocol to websocket
Add cross compiling with 'TARGET='
Fix some issues with ARM

New proxy code in spg_auth.
Moved all trackers to new interface
Cleanup some old stuff.