Beginning RowRange implementation.

Stubbing out iterators.
Implementing some basic iterator operations.
Starting them out as ForwardIterator for simplicity.
Completing const iterator.
Implementing non-const iterator.

Fixing assertion failure upon end() call.
Fixing incorrect equality comparisons.

Factoring iterator inheritance correctly.
Fixing off-by-one error in iterator bounds.

Fixing dereference operators.
Placing inside cv namespace.
Removing unused typedefs.