Refs #8140 Add methods to validate widget input and check state.
Refs #8140 Updated UserInputValidator to support widget

Also made use of added functions in Fury for testing.
Merge remote-tracking branch 'origin/feature/8140_dataselector_validation_options'
Merge branch 'master' of github.com:mantidproject/mantid
Merge branch 'master' of github.com:mantidproject/mantid
Re #8436. Renamed HWHWM to FWHM in Lorentzian.
Re #8436. Corrected ConvFit page.
Re #8436. Refactored RangeSelector to prevent signal loops.
Re #8436. Update range selector on ConvFit when peak centre moves.
Merge remote-tracking branch 'origin/feature/8436_rename_Lorentzian_HWHM_to_FWHM'