toolhead: Add a move.move_error() helper

Move the EndstopMoveError() code from homing.py to a new method in the
toolhead Move class.

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

klippy/homing.py

@@ -164,8 +164,4 @@ class CommandError(Exception):
 class EndstopError(CommandError):
     pass
 
-def EndstopMoveError(pos, msg="Move out of range"):
-    return EndstopError("%s: %.3f %.3f %.3f [%.3f]" % (
-            msg, pos[0], pos[1], pos[2], pos[3]))
-
 Coord = collections.namedtuple('Coord', ('x', 'y', 'z', 'e'))