gremlin.py: define change_tool() in class StatCanon

add def for change_tool() so that both:
     GLCanon.change_tool() and StatMixin.change_tool()
are executed (as is the usage in axis.py)

GLCanon.change_tool()   only affects first_move
StatMixin.change_tool() updates tools[]
sim_pin script to simulate writing to hal pin

Supports multiple pins with three modes available for each:
  1) OnePulse
  2) ToggleValue
  3) 1 WhilePressed

Usage:
       sim_pin pin_name1 [pin_name2 ...] &

Note:  linuxcnc must be running
       The pin(s) may not be connected to a signal
Merge branch 'v2.5_branch'
gscreen -add a function to get linuxcnc's current mode
gscreen -remove references to numerical entry widget

Now the popup numerical entry widget will be used.
gascreen config -remove entry widget from screen