systat - Refactor memory displays for systat -vm

systat - Refactor memory displays for systat -vm

* Report paging and swap activity in bytes and I/Os instead of pages and
  I/Os (I/Os usually matched pages).

* Report zfod and cow in bytes instead of pages.

* Replace the REAL and VIRTUAL section with something that makes a bit
  more sense.

  Report active memory (this is just active pages), kernel memory
  (currently just wired but we can add more stuff later), Free
  (inactive + cache + free is considered free/freeable memory), and
  total system memory as reported at boot time.

  Report total RSS - basically how many pages the system is mapping to
  user processes.  Due to sharing this can be a large value.

  Do not try to report aggregate VSZ as there's no point in doing so
  any more.

  Reported swap usage on the main -vm display as well as total swap
  allocated.

* Fix display bug in systat -sw display.

* Add "nvme" device type match for the disk display.