STYLE: code cleanup searchableSurface (issue #929)

- improve doxygen entries for searchable surfaces.

- support selection of searchable surfaces with shorter names.
  Eg,
      type   box | cylinder | ...;
  vs  type   searchableBox | searchableCylinder | ...;

tutorials/mesh/foamyHexMesh/simpleShapes/system/foamyHexMeshDict

@@ -34,11 +34,10 @@ geometry
     // Outside of domain
     domain
     {
-        type searchableBox;
-        min (-0.7 -0.9 -1);
-        max (1.3 1.1 1);
+        type box;
+        min  (-0.7 -0.9 -1);
+        max  (1.3 1.1 1);
     }
-
 }