TypeAndDataManager:  Added some basic iterators to simplify core TADM routines.

The iterators are designed to compile to the same code as the original C code. But the implementation is
now in the templates. This is a first step to adding iterator primitives to vireo in general.
TADM: Removed some old #ifdef code.
TADM: reordered _capacity field in TypedArayCore

Preparing for base class refactoring for TypedArrayCore