tristate group widget

Tristate Switch control (group)

Group control using the same code as my script widget (avaialble at https://github.com/stam66/tristate/tree/Final).

As this is not a widget, this is implemented with a stack to create new and modify existing tristate controls (best use as a plugin, just drop into the plugin folder and restart).

Short note about usage and tooltips available the stack. If any problems, please raise an issue on the GitHub page above.