Refs #7853. Add new class for dealing with auto-saving values.
Refs #7853. Add auto-saver to Options Tab code.
Refs #7853. Move simplest save signals to auto-saver.
Refs #7853. Move validator creation function to helper source.
Refs #7853. Use validators instead of manual validation.
Refs #7853. Replace more saving slots with auto-saver.
Refs #7853. Move more auto-saving to auto-saver.
Refs #7853. Fix auto-saver declaration.
Refs #7853. Move last widgets to auto-saver.
Refs #7853. Remove another redundant slot.
Refs #7853. Fix names and docs of slots which are here to stay.

Plus some other style improvement here and there.
Refs #7853. Make it possible to enabled auto-saving later.

So that we can e.g. load saved values before auto-saving is enabled.
Refs #7853. Add methods to load values and use them on the tab.

Remove code to load settings tab widgets from MuonAnalysis source.
Refs #7853. Add method to enabled/disable saving for one widget only.
Refs #7853. Refactor time axis slot.
Refs #7853. Refactor autoscale slot.
Refs #7853. Remove unused members.
Refs #7853. Change the way check-box values are saved.

Boolean type seems more natural.
Refs #7853. Call slots manually after loading saved values.
Refs #7853. Move irrelevant slots out of the tab class.