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
select the kinematics with G12.1, which
synchronizes interpreter and motion
itself.

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
