Merge to ensure CrystalFieldFunction is available and up to date.

Might give 5-10% speedup of init of MatrixWorkspace (pending follow-up
uncommitted changes).

This reverts commit ac1bab4b.

The problem is that while IndexInfo is not meant for threaded use from
within an Algorithm, we must always support it: Multiple algorithms may
be running at the same time and SpectrumNumberTranslator may be shared
between workspaces.

Sorting late to avoid general slowdown (now sorting only when map access
needed).