- As the names describe, check if the string starts or ends with a
  particular value. Always true if the given text is empty or if the
  string is identical to the given text.

   - add an extension to the file name
   - remove a file extension
   - check if a file name has an extension
   - check if a file name has a particular extension (as word),
     or matches a particular grouping of extensions (as wordRe).

This slightly more convenient when working with char[] input:

     fileName file1{ "path", "name", "to", "file.ext" };
vs.  fileName file1 = fileName(path)/"name"/"to"/"file.ext";

But is a bit more efficient since it avoid most of the intermediate
copying and resizing incurred by the '/' operator.

- not required for ASCII, and makes normal dictionaries too noisy.

STYLE: move archHint to be a file-scope static

- Use wordRe::REGEXP (not wordRe::DETECT) if the content is known to
  be a regular expression anyhow.

Bounding thermo.rho in rhoPorousSimpleFoam.
Changing initial time step in externalSolarLoad tutorial.
Commenting out momemtun source term in steamInjection which causes problems

  FoamFile
  {
      version     2.0;
      format      binary;
      arch        "LSB;label=32;scalar=64";
      class       vectorField;
      object      points;
  }

There is otherwise no simple indication in any of the files as to the
sizes used (Int32 vs Int64, SP vs DP). This makes it difficult for the
end-user and also for any third-party consumers.

--
The architecture information contains three items in the following format:

    (LSB|MSB);label=(32|64);scalar=(32|64)

- The endian value always appears first, without any leading space.
  This make it trivial to check later. Either the first 3 letters (LSB
  vs MSB) or even just the first letter ('L' vs 'M').

- Subsequent key=value pairs for 'label' and 'scalar' are separated
  by semicolons. The ordering of label vs scalar is not specified.

Note that this 'arch' information is purely informational.
It is currently not used by the OpenFOAM input mechanism itself.

- can adjust many more values

- sometimes used for off-screen rendering.
  Only add to library-path when they are actually available

added optional argument description (Fixes #347)

Optional argument listed.

@andy @mark Could you confirm/merge?

See merge request !90