ENH: provide dictionary access for coded BCs etc (#1922)

- in some cases, additional dictionary inputs are useful for extending
  the input parameters or functionality of dynamic coded conditions.

  Typically this can be used to provide a simple set of dictionary
  inputs that are used to drive specific code, but allows changing the
  inputs without causing a recompilation.

  Accessed with this type of code:
  ```
  const dictionary& dict = this->codeContext();
  ```

boundary conditions and function objects:

* specify an additional codeContext dictionary entry:
  ```
  codeContext
  {
      ...
  }
  ```

PatchFunction1:

* The code context dictionary is simply the dictionary used to specify
  the PatchFunction1 coefficients.

  To replicated persistant data, use local member static data.
  Eg,
  ```
  code
  #{
      // Persistent (Member) Data
      static autoPtr<Function1<scalar>> baseVel;
      static autoPtr<Function1<vector>> baseDir;
      ...
  #}
  ```

fvOptions:

* currently not applicable

src/meshTools/PatchFunction1/CodedField/CodedField.H

@@ -70,6 +70,10 @@ Usage
     }
     \endverbatim
 
+Note
+    The code context dictionary is simply the dictionary used to specify
+    the PatchFunction1 coefficients.
+
 See also
     Foam::dynamicCode
     Foam::codedFixedValue
@@ -132,6 +136,9 @@ protected:
         //- Clear redirected object(s)
         virtual void clearRedirect() const;
 
+        //- Additional 'codeContext' dictionary to pass through
+        virtual const dictionary& codeContext() const;
+
         // Get the code (sub)dictionary
         virtual const dictionary& codeDict(const dictionary& dict) const;