ENH: additional #word and #message dictionary directives (#2276)

- use `#word` to concatenate, expand content with the resulting string
  being treated as a word token. Can be used in dictionary or
  primitive context.

  In dictionary context, it fills the gap for constructing dictionary
  names on-the-fly. For example,

  ```
  #word "some_prefix_solverInfo_${application}"
  {
      type    solverInfo;
      libs    (utilityFunctionObjects);
      ...
  }
  ```

  The '#word' directive will automatically squeeze out non-word
  characters. In the block content form, it will also strip out
  comments. This means that this type of content should also work:

  ```
  #word {
     some_prefix_solverInfo
     /* Appended with application name (if defined) */
     ${application:+_}  // Use '_' separator
     ${application}     // The application
  }
  {
      type    solverInfo;
      libs    (utilityFunctionObjects);
      ...
  }
  ```
  This is admittedly quite ugly, but illustrates its capabilities.

- use `#message` to report expanded string content to stderr.
  For example,

  ```
  T
  {
     solver          PBiCG;
     preconditioner  DILU;
     tolerance       1e-10;
     relTol          0;
     #message "using solver: $solver"
  }
  ```
  Only reports on the master node.

applications/test/dictionary/testDict

@@ -18,6 +18,8 @@ FoamFile
 #sinclude   "$FOAM_CASE/someUnknownFile"
 #includeIfPresent "$FOAM_CASE/someUnknownFile-$FOAM_CASENAME"
 
+zeroVelocity    uniform (0 0 0);
+
 internalField   uniform 1;
 
 // supply defaults
@@ -48,7 +50,7 @@ x 5;
 varName x;
 
 
-//Indirection for keys
+// Indirection for keys
 key inlet_9;
 
 
@@ -67,13 +69,17 @@ boundaryField
     inlet_5  { $inactive }
     inlet_6a { $...inactive }   // Relative scoping - fairly horrible to use
     inlet_6b { $^inactive }     // Absolute scoping
+    inlet_6c { key ${/key}; }   // Absolute scoping
+
     inlet_7  { ${inactive}}     // Test variable expansion
     inlet_8  { $inactive }
+
+    // Variable expansion for a keyword
     ${key}   { $inactive }
 
     #include "testDictInc"
 
-    outlet
+    outletBase
     {
         type            inletOutlet;
         inletValue      $internalField;
@@ -83,16 +89,36 @@ boundaryField
         y               6;
     }
 
-    // this should have no effect
+    outlet
+    {
+        $outletBase
+    }
+
+    Default_Boundary_Region
+    {
+        valueOut        $zeroVelocity;
+    }
+
+    // this should have no effect (not in scope)
     #remove inactive
 
-    inlet_7  { ${${varType}}}   // Test indirection/recursive expansion
-    inlet_8  { $active }
+    // But this should work to remove things in different scopes
+    #remove "/zeroVelocity"
+
+    inlet_7  { ${inactive} }    // Test variable expansion
+    inlet_8  { $inactive }
+
+    inlet_7a { ${${varType}} }  // Test indirection/recursive expansion
+    inlet_7b { ${${varType}} }  // Test indirection/recursive expansion
 
     #overwrite inlet_8  { type none; }
 }
 
 
+// No patterns with scoped removal
+// #remove "/boundaryField/outletB.*"
+#remove "/boundaryField/outletBase"
+
 #include "testDict2"
 
 verbatim #{
@@ -123,10 +149,25 @@ baz
     $active
 }
 
-// this should work
-#remove active
+// This should work
+#remove x
 
-// this should work too
+// This should work too
 #remove ( bar baz )
 
+// Remove a sub-dictionary entry
+#remove "/anynumber.*/value"
+
+// Removal does not auto-vivify
+#remove "/nonExistentDict/value"
+
+// Add into existing dictionary
+"/anynumber.*/someValue"  100;
+
+// Auto-vivify
+// - but currently cannot auto-vivify entries with dictionary patterns
+"/abd/someValue"    100;
+"/def/'someValue.*" 100;
+
+
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //