- both autoPtr and tmp are defined with an implicit construct from
  nullptr (but with explicit construct from a pointer to null).
  Thus is it safe to use 'nullptr' when returning an empty autoPtr or tmp.

Improve alignment of its behaviour with std::shared_ptr

  - element_type typedef
  - swap, reset methods

* additional reference access methods:

cref()
    returns a const reference, synonymous with operator().
    This provides a more verbose alternative to using the '()' operator
    when that is desired.

        Mnemonic: a const form of 'ref()'

constCast()
    returns a non-const reference, regardless if the underlying object
    itself is a managed pointer or a const object.
    This is similar to ref(), but more permissive.

        Mnemonic: const_cast<>

    Using the constCast() method greatly reduces the amount of typing
    and reading. And since the data type is already defined via the tmp
    template parameter, the type deduction is automatically known.

    Previously,

        const tmp<volScalarField>& tfld;

        const_cast<volScalarField&>(tfld()).rename("name");
        volScalarField& fld = const_cast<volScalarField&>(tfld());

    Now,

        tfld.constCast().rename("name");
        auto& fld = tfld.constCast();

--

BUG: attempts to move tmp value that may still be shared.

- old code simply checked isTmp() to decide if the contents could be
  transfered. However, this means that the content of a shared tmp
  would be removed, leaving other instances without content.

* movable() method checks that for a non-null temporary that is
  unique (not shared).

This change requires that the de-reference operator '()' returns a
const-reference to the object stored irrespective of the const-ness of
object stored and the new member function 'ref()' is provided to return
an non-const reference to stored object which throws a fatal error if the
stored object is const.

In order to smooth the transition to this new safer 'tmp' the now
deprecated and unsafe non-const de-reference operator '()' is still
provided by default but may be switched-off with the compilation switch
'CONST_TMP'.

The main OpenFOAM library has already been upgraded and '-DCONST_TMP'
option specified in the 'options' file to switch to the new 'tmp'
behavior.  The rest of OpenFOAM-dev will be upgraded over the following
few weeks.

Henry G. Weller
CFD Direct

Function1 is an abstract base-class of run-time selectable unary
functions which may be composed of other Function1's allowing the user
to specify complex functions of a single scalar variable, e.g. time.
The implementations need not be a simple or continuous functions;
interpolated tables and polynomials are also supported.  In fact form of
mapping between a single scalar input and a single primitive type output
is supportable.

The primary application of Function1 is in time-varying boundary
conditions, it also used for other functions of time, e.g. injected mass
is spray simulations but is not limited to functions of time.

Removed inconsistent binary output.
Removed unused and IO-inconsistent functions.
Simplified the handling of backward-compatible constant value:
    Removed the unnecessary CompatibilityConstant,
    Updated Constant and DataEntryNew to handle constant value construction.

The new NotImplemented macro uses __PRETTY_FUNCTION__ for GNU compatible
compilers otherwise __func__ to provide the function name string.

This allows for more than one of these data types to be specified in a dictionary
Resolves bug-report http://www.openfoam.org/mantisbt/view.php?id=1652

e.g.
        <entryName> csvFile;
        <entryName>Coeffs
        {
            nHeaderLine         4;
            refColumn           0;          // reference column index
            componentColumns    (1 2 3);    // component column indices
            separator           ",";        // optional (defaults to ",")
            mergeSeparators     no;         // merge multiple separators
            fileName            "fileXYZ";  // name of csv data file
            outOfBounds         clamp;      // optional out-of-bounds handling
            interpolationScheme linear;     // optional interpolation scheme
        }

STYLE: move DataEntry to OpenFOAM/primitives/functions

This reverts commit c5bea524.

This reverts commit b18f6cc1.