- ensures that read failures can be properly detected

COMP: include refPtr.H instead of autoPtr.H in IOobject.H

- ensures inclusion of autoPtr/refPtr/tmp/stdFoam

ENH: add IOobject::resetHeader() method

- when re-using an IOobject for repeated read operations it enforces
  resetting of headerClassName, scalar/label sizes etc prior to
  reading. Permits convenient resetting of the name too (optional).

  Example,

      IOobject rio("none", ..., IOobject::LAZY_READ);

      rio.resetHeader("U")
      if (returnReduceOr(rio.typeHeaderOk<volVectorField>(false)))
          ...

      io.resetHeader("p")
      if (returnReduceOr(rio.typeHeaderOk<volScalarField>(false)))
         ...