kcollect - Implement gnuplot output feature

kcollect - Implement gnuplot output feature

* Implement the gunplot output feature.  This feature currently
  hard-selects a set of fields (fields cannot be specified).

  Generates two graphs.  The first collects memory statistics
  and machine load.  The second collects cpu utilization and
  fault, syscall, and nlookup (file path resolution) rate.

* In gnuplot output mode, -f will cause the entire dataset to be
  regenerated every 60 seconds (I don't see any way to avoid this
  to update an existing gnuplot window).

* Finish implementing -o fields