Changed handling of homing inputs from limit switches.

Some drivers will now only disable hard limits (if enabled) for axes that are homing, this includes max/min limit switches.
HAL entry points and core handlers/events has been added and some have changed signatures in order to better support kinematics implementations.
More work on delta kinematics: new and changed settings, some improved functionality. Still in progress.

machine_limits.h

@@ -33,6 +33,8 @@ typedef enum
     HomingMode_Pulloff
 } homing_mode_t;
 
+void limits_init (void);
+
 // Perform one portion of the homing cycle based on the input settings.
 status_code_t limits_go_home (axes_signals_t cycle);