gscreen -modify cycle start method so gscreen can use it

This file was based from TOUCHY's, some of the methods are still unchanged.
The cycle start method was not used till now.
This method is currently used when the cycle-start pin is changed true.
If in paused mode then it will single step the program else start from
the beginning. I may wish to include run-from-line later
gscreen -add a cycle-start HAL pin

When pin changes to true:
if in MDI mode the command in the MDI text box will be executed.
if in AUTO mode the program will be started or stepped depending
on whether linuxcnc is paused or not.