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/test/findCell-octree/Test-findCell-octree.C

@@ -45,7 +45,7 @@ int main(int argc, char *argv[])
 
     label nReps = 10000;
 
-    const point sample = args.argRead<point>(1);
+    const point sample = args.read<point>(1);
 
     const polyMesh::cellDecomposition decompMode = polyMesh::CELL_TETS;