- NestTF refactored to cover all package items
- fixed issue where type traverse skipped typedefs

This also entailed further fleshing out the expression traversal helper
to cover expressions in generate blocks, which could, of course, use
$bits.

This should make it much easier to add support for ``, `", macros with
arguments, etc., in the future.

significant refactor of packed array flatten conversion; now supports module items in generate blocks