Details:
- Implemented bli_acquire_mpart(), a general-purpose submatrix view
function that will alias an obj_t to be a submatrix "view" of an
existing obj_t.
- Renumbered examples in examples/oapi and inserted a new example file,
03obj_view.c, which shows how to use bli_acquire_mpart() to obtain
submatrix views of existing objects, which can then be used to
indirectly modify the parent object.
