Memory map attribute changes.
Memory map attribute changes.

- Added sector_size attribute alias of blocksize.
- Added is_nonsecure attribute default.
- Changed to using DEFAULT_ATTRS for all default region attribute values
  in subclasses.

mesheven/pyOCD,mbedmicro/pyOCD,mesheven/pyOCD,mbedmicro/pyOCD,pyocd/pyOCD,mesheven/pyOCD,flit/pyOCD,pyocd/pyOCD,flit/pyOCD,mbedmicro/pyOCD