2extrajoints demo

Demo of the motmod num_extrajoints= parameter

a) XYYZ correspond one-to-one to
   joints 0123
b) joint.4 and joint.5 are 'extra'
   joints not related to any axis
   letter but managed independently by
   limit3 components.
c) The configuration uses basic_sim.tcl
   and simulates home switches for all
   joints.
d) Using extra joints requires
   NON-identity kinematics and all
   joints (including joint4) must be
   homed before switching to world
   mode.
e) A halshow app is opened to display
   key pin values
f) A sim_pin app is opened to set key
   pin values

Usage:
1) F1        (Estop Off)
2) F2        (Machine On)
3) optionally jog joint.4 and joint.5
   prior to homing to observe motor
   offset
4) Ctrl-HOME (Home all)
5) demonstrate joint.[45] movement
   using the provided M144 mdi
   command:
   M144 P4 Q1.23 move joint.4 to 1.23
   M144 P4 Q4.56 move joint.4 to 4.56
   M144 P5 Q3.21 move joint.5 to 3.21
   M144 P5 Q2.22 move joint.5 to 2.22
   etc.
6) Alternately, demonstrate joint.[45]
   movement using sim_pin settings:
     j4.limit3.min  min value
     j4.limit3.max  max value
     j4.limit3.maxv max velocity
     j4.limit3.maxa max acceleration
     j4.limit3.in   requested value
     similar for j5