Require optional properties to be present in subtypes
Remove unused getBestCommonType method (unrelated change)
Accepting new baselines
Adding missing blank
Merge branch 'master' into optionalPropertySubtyping

Conflicts:
	tests/baselines/reference/arrayLiteralWithMultipleBestCommonTypes.types
Merge pull request #919 from Microsoft/optionalPropertySubtyping

Require optional properties to be present in subtypes