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- use FixedList first/last in Pair first/second

- consistent first/second access for line

- provide shorter versions: pointIndList, pointUIndList, etc.
  and indirect versions of commonly used types:
     labelIndList, scalarIndList, vectorIndList

- simplifies organization, allows reuse.
  provide some other useful hash types.

Avoids the clutter and maintenance effort associated with providing the
function signature string.

This reverts commit c5bea524.

This reverts commit b18f6cc1.

- If the underlying type is contiguous, FixedList hashes its storage directly.
- Drop labelPairHash (non-commutative) from fvMeshDistribute since
  FixedList::Hash does the right thing anyhow.
- Hash<edge> specialization is commutative, without multiplication.
- Hash<triFace> specialization kept multiplication (but now uLabel).
  There's not much point optimizing it, since it's not used much anyhow.

Misc. changes

- added StaticAssert to NamedEnum.H
- label.H / uLabel.H : define FOAM_LABEL_MAX, FOAM_ULABEL_MAX with the
  values finally used for the storage.  These can be useful for pre-processor
  checks elsewhere (although I stopped needing them in the meantime).

- grammar in comments, namespace qualifiers, etc.