Make CalculateResolution output TwoTheta.

Refs #10198.
Update the value of TwoTheta in refl_gui's table.

Refs #10198.
Merge branch 'feature/10198_place_value_of_twotheta_into_refl_table' into develop

Conflicts:
	Code/Mantid/scripts/Interface/ui/reflectometer/refl_gui.py