ENH: adjust renumbering methods, extend renumberMesh options

Update to renumber methods. The user-exposed aspect is in the renumberMesh application which now has additional options.

• Use -dry-run with -write-maps to visualize the before/after effects of renumbering (creates a VTK file).
• The -no-fields option to renumber the mesh only. This is useful and faster when the input fields are uniform and the -overwrite option is specified.
• The -renumber-method allows a quick means of specifying a different default renumber method (instead of Cuthill-McKee).
• The -renumber-coeffs option allows passing of dictionary content for the method.

Examples,

// Different ways to specify reverse Cuthill-McKee

  -renumber-method RCM
  -renumber-coeffs 'reverse true;'
  -renumber-method CuthillMcKee
  -renumber-coeffs 'reverse true;'
  -renumber-coeffs 'method CuthillMcKee; reverse true;'

// Other (without dictionary coefficients)
  renumberMesh -renumber-method random

// Other (with dictionary coefficients)
   renumberMesh \
      -renumber-method spring \
      -renumber-coeffs 'maxCo 0.1; maxIter 1000; freezeFraction 0.99;'

// Other (with additional libraries)
   renumberMesh -renumber-method zoltan -lib zoltanRenumber

The new -decompose option permits a region-wise decomposition prior to renumbering. The effects of this can be seen in the following

The original cells are randomly numbered. With the -decompose option, these can be "lumped" into regions before renumbering on a per region basis. If the region-wise renumbering is forcibly disabled (ie, -renumber-method none), it can be seen that the resulting cellIds retain the random nature of the original cell ordering. This corresponds to what decomposePar without a subsequent renumber would do, so could be indicative that an optional renumber stage would be reasonable to add into decomposePar in the future.