ENH: regIOobject store() now also registers the object

• previously the store() method just set the ownedByRegistry flag. Now ensure that it is indeed registered first.

• support register/store of tmp<> items. The tmp parameter is not cleared, but changed from PTR to CREF to allow further use.

  The implicit registration allows code simplification using the GeometricField::New factory method, for example.

  Old Code

  volScalarField* ptr = new volScalarField
  (
      IOobject
      (
          fieldName,
          mesh.time().timeName(),
          mesh,
          IOobject::NO_READ,
          IOobject::NO_WRITE,
          true  // Register
      ),
      mesh,
      dimless,
      zeroGradientFvPatchField<scalar>::typeName
  );
  ptr->store();

  New Code

  auto tptr = volScalarField::New
  (
      fieldName,
      mesh,
      dimless,
      zeroGradientFvPatchField<scalar>::typeName
  );
  regIOobject::store(tptr);

  or even regIOobject::store ( volScalarField::New ( fieldName, mesh, dimless, zeroGradientFvPatchField::typeName ) );