Remove floating windows for control point info and ruler, replacing with always updated top level one.

    Checkpoint commit for WIP.
    
    Remove floating control point window, unifiy with reguler ruler info.
    Move floating ruler window info to Measure Tool Window (under Window).
    Update info when ruler is not active.
    Update ruler segement intersections on spline changes.
    Allow snapped ruler ends to follow snapped points.
    
    Convert to snprintf().
    Use M_PI.