interpolator: force REQUEST_STATE to send 8 bytes, because 4 bytes won't get flushed through the driver.
webapp: fixed tool position feedback code, added white background behind the iframe
code planner: speed improvment
 - overhaul in CPS of planner to limit data copies
 - use web worker to limit UI blocking
 - work queue for USB bulk data to start sending immediately
 - state polling instead of event handling (some events get lost)