added new gcode settings:
 * start/stop spindle (M3/M5)
 * path mode (G61/G61.1/G64)
moved gcode settings to the general program preferences


git-svn-id: https://pycam.svn.sourceforge.net/svnroot/pycam/trunk@633 bbaffbd6-741e-11dd-a85d-61de82d9cad9