gcode: Split G0/G1 command handling to new gcode_move class

Split up the main GCodeParser class into GCodeDispatch and GCodeMove
classes.  The GCodeMove class is now available using the "gcode_move"
printer object name.  This split simplifies the gcode.py code.

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

klippy/extras/virtual_sdcard.py

@@ -24,7 +24,6 @@ class VirtualSD:
         self.work_timer = None
         # Register commands
         self.gcode = printer.lookup_object('gcode')
-        self.gcode.register_command('M21', None)
         for cmd in ['M20', 'M21', 'M23', 'M24', 'M25', 'M26', 'M27']:
             self.gcode.register_command(cmd, getattr(self, 'cmd_' + cmd))
         for cmd in ['M28', 'M29', 'M30']: