refs #10333. Work around NeXus bug.

Fixed and enabled tests that Russell previously disabled.

Extracted confidence functionality and exposed as a static public class member.

Give good, but not excellent confidence for restricted partial string matches with NXSPE.

Added extra tests for the confidence funtionality.
refs #10333. Merge in master and fix conflicts.

Merge branch 'master' into feature/10333_osx_nxspe

Conflicts:
	Code/Mantid/Framework/DataHandling/src/LoadNXSPE.cpp
Merge pull request #48 from mantidproject/feature/10333_osx_nxspe

Feature/10333 osx nxspe