Feature ioobjectlist registry

- support name filtering by class based on <Type> or predicates.
  Eg,

      objects.sortedNames<volScalarField>(namePattern);
  vs  objects.sortedNames(volScalarField::typeName, namePattern);

  These can also be used directly for untyped name matching.
  Eg,
      objects.sortedNames<void>(namePattern);

  Can also use a predicate:

      objects.sortedNames(wordRe("vol.*Field"), namePattern);
      objects.sortedNames
      (
          [](const word& clsName){ return clsName.startsWith("vol"); },
          namePattern
      );

- add IOobjectList::count() methods

- lookupClass<Type>() to use types instead of class variables.

- additional helpers for parallel: allNames(), checkNames()

- provide filterClasses() and filterObjects(), prune_0() method
  forwarding to HashTable methods for easier access.

- can be useful for obtaining information about number of fields.
  Eg,

       nScalar = mesh.count<volScalarField>(wordre);

- replace explicit use of wordRe, wordRes, wordHashSet as filters
  with a MatchPredicate.

- support filtering by class based on <Type> or predicates