puma560-switchkins usage:

1) startup (after homing) is in
genserkins mode configured like
puma560.ini as an inch-based machine
with 6 revolute joints.

2) pyvcp buttons are provided to switch
between genserkins and identity
kinematics.  The buttons issue remapped
commands M428,M429.  These commands a)
set the motion.switchkins-type pin and
b) force a synchronization using a
motion input read command.

3) when set for identity kins, default
assignments are:

   x : joint0
   y : joint1
   z : joint2
   a : joint3
   b : joint4
   c : joint5
so the gcode commands:
   'g0x10' moves joint0
   'g0c10' moves joint5

4) the ordering can be altered using the
genser-switchkins kinematics module
parameter 'coordinates'.  For example,

KINEMATICS=genser-switchkins coordinates=abcxyz

assigns:
   a : joint0
   b : joint1
   c : joint2
   x : joint3
   y : joint4
   z : joint5
so the gcode commands:
   'g0x10' moves joint3
   'g0c10' moves joint2
