Re #6577. Revert changes to sfCalculator.py under this ticket.

This is the sfCalculator found in scripts/LargeScaleStructures/ScalingFactorCalculation/.
It was already migrated to the v2 API under a different ticket (#6576).

This partially reverts commit bf341994ea58cded8623c9cc79c7d9951f50d44e.
Re #6577. Python algorithm location has moved since branch started.
Re #6577. Update algorithm subscription call.
Re #6577. Remove commented out imports.

Will avoid clutter when we're searching for the final remaining
imports of the old API in the codebase.
Re #6577. Remove first attempted port to v2 API.

This algorithm was partially ported to v2 but the old version was left
in place and is picked up first. This one still needs more done to
make it work with v2 so the work will be started over under #7404.
Merge branch 'feature/6577_reduction_gui' into develop

Conflicts:
	Code/Mantid/scripts/LargeScaleStructures/ScalingFactorCalculation/sfCalculator.py