homing: Create Homing class from gcode

Create the Homing class in the gcode handler instead of in the
kinematic classes.  This will make it easier to pass error messages
back to the user.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

klippy/toolhead.py

@@ -259,16 +259,15 @@ class ToolHead:
             self.extruder.check_move(move)
         self.commanded_pos[:] = newpos
         self.move_queue.add_move(move)
-    def home(self, axes):
-        homing = self.kin.home(self, axes)
-        def axes_update(axes):
+    def home(self, homing_state):
+        self.kin.home(homing_state)
+        def axes_update(homing_state):
             pos = self.get_position()
             homepos = self.kin.get_homed_position()
-            for axis in axes:
+            for axis in homing_state.get_axes():
                 pos[axis] = homepos[axis]
             self.set_position(pos)
-        homing.plan_axes_update(axes_update)
-        return homing
+        homing_state.plan_axes_update(axes_update)
     def dwell(self, delay):
         self.get_last_move_time()
         self.update_move_time(delay)