Re #5896. Use new-style PyQt signal-slot connection syntax.
Re #5896. A mechanism to change settings when live button is pressed.

Some settings are not applicable or need to have certain values for
live reduction. This allows other settings (even in different tabs)
to be set or disabled when the live button is pressed.
Re #5896. Fix certain settings in DGS gui when live button pressed.

This fixes the values of certain aspects and disables the gui elements
when the live button is depressed. Any changed settings are remembered
and reverted when the button is unchecked.
Re #5896. Spelling correction.