location for the specification is the same as that for the pd level.

- explicitly remove any previously decomposed 'mut' and 'nut' when
  decomposing fields since they can otherwise prevent the turbulence model
  from being upgraded properly.
  Removing all decomposed fields first might be a better idea in the
  long-term, but would probably be slower.

- added constructor dictionary(const dictionary*) that also handles NULL
  pointers and makes it convenient to construct from a possibly nonexistent
  sub-dictionary:
  eg,
      dictionary dict2(dict1.subDictPtr("someDict"));

- make some of the turbulence Coeffs sub-dictionary optional.
  Their contents are all 'lookupOrAddDefault' anyhow.

- in turbulentMixingLength BCs, skip namespace qualifier in template
  (eg, <RASModel> vs. <compressible::RASModel>)

- change comments from 'turbulenceProperties' to RASProperties/LESProperties

- consistency between compressible/incompressible - no separate file for
  'New' selector etc

- consistency in accessing the model coefficients.
  Use method coeffDict() for const access.
  Use protected data member coeffDict_ for read/write access.

- document model coefficients in etc/constant/RASProperties.
  Need the same for LESProperties before we can prune these from the
  tutorials.

- #inputMode error
  now issues a FatalError on duplicate entries

- #inputMode warn
  issues a warning on duplicate entries, corresponds to the
  old behaviour of 'error'

- #inputMode protect
  prevents overwriting existing entries

The 'protect' mode provides a simple mechanism for supplying default values.
eg,
    in file1:
        #inputMode  protect
        intensity       0.1;
        mixingLength    0.005;
        #inputMode  merge

        inlet
        {
            type        turbulentIntensityKineticEnergyInlet;
            intensity   $intensity;
        }

    which is included from file2:

        intensity   0.05;
        #include    "file1"

- createBaffles used List::append(const T&), changed to DynamicList

- DynamicList gets append methods as per List
- misc cosmetic changes

Changing FreeStream to create inflow on all patches of type patch.  Implemented Bird eqn 4.22 for the number flux and eqn 12.5 for the velocity distibution.  Drawing T and U for the FreeStream from the boundaryT and boundaryU fields.