natural sort instead of ASCII-based sorting, so that ports that
are numbered arrays will be indexed properly by count. Also:
Modified the "extresist" handling of substrate to draw the default
substrate type over the entire cell area (less areas of nwell or
other conflicting type). This allows extresist to extract the
entire substrate as a resistive network. The result is ugly and
may warrant some aggressive network simplification, but it should
at least be realistic.