Re #6371. Check whether the input table is empty, fail if it is.

The algorithm previously would fail, but with a cryptic error message
at the point it tried to create the output workspace. This is more
obvious.
Re #6371. Don't remove the row for scan_index=1 if it's the only one.
Re #6371. Add code to allow use with live data.
Re #6371. Well it worked for me...
Optional output workspace for DakotaChiSquared. Refs #6823
Merge branch 'feature/6823_DakotaChiSquared_output' into develop
Re #6371. Left in a local testing line by mistake.

Also temporarily remove check that logs have more than one value
for testing live client.
Merge branch 'feature/6371_step_scan_gui' into develop
Re #6371. Temporarily remove assert while testing live.
Merge branch 'feature/6371_step_scan_gui' into develop
Re #6371. Always enable live button pending debugging of that code.
Merge branch 'feature/6371_step_scan_gui' into develop
Merge branch 'bugfix/6449_fixMDBoxSplittingPerformance' of https://github.com/mantidproject/mantid into develop
Merge branch 'Branch_bugfix/6449_fixMDBoxSplittingPerformance' into develop
Merge branch 'Branch_bugfix/6449_fixMDBoxSplittingPerformance' into develop
Merge branch 'Branch_bugfix/6449_fixMDBoxSplittingPerformance' into develop
Merge branch 'Branch_bugfix/6449_fixMDBoxSplittingPerformance' into develop
Merge branch 'Branch_bugfix/6449_fixMDBoxSplittingPerformance' into develop
Merge branch 'Branch_bugfix/6449_fixMDBoxSplittingPerformance' into develop
Merge branch 'Branch_bugfix/6449_fixMDBoxSplittingPerformance' into develop