ENH: simplify method names for reading argList options and arguments

- use succincter method names that more closely resemble dictionary
  and HashTable method names. This improves method name consistency
  between classes and also requires less typing effort:

    args.found(optName)        vs.  args.optionFound(optName)
    args.readIfPresent(..)     vs.  args.optionReadIfPresent(..)
    ...
    args.opt<scalar>(optName)  vs.  args.optionRead<scalar>(optName)
    args.read<scalar>(index)   vs.  args.argRead<scalar>(index)

- the older method names forms have been retained for code compatibility,
  but are now deprecated

applications/utilities/mesh/manipulation/splitMesh/splitMesh.C

@@ -129,7 +129,7 @@ int main(int argc, char *argv[])
     const word setName = args[1];
     const word masterPatch = args[2];
     const word slavePatch = args[3];
-    const bool overwrite = args.optionFound("overwrite");
+    const bool overwrite = args.found("overwrite");
 
     // List of faces to split
     faceSet facesSet(mesh, setName);