refs #6841 as MDEvent test helper has experiment info now,

FakeMDTest can not add one. Hopefully fixed.
Merge branch 'feature/6841_MergeMDAddsExperimentInfo' of https://github.com/mantidproject/mantid into develop
refs #6841 some typing error
Merge branch 'feature/6841_MergeMDAddsExperimentInfo' into develop