fix missing assignment
JRB-26 more work on a clean sync/shutdown

- add a thread factory to name the threads something useful
- only initialize the executor if a read-write RrdNioBackend
  is open()'d
- add an explicit shutdown() method for shutting down the
  executor before finalize() does
format
Yet another JRB-26 fix, this time using reference-counting.
make a startSchedule() method so it is more obvious what happens where
a bit more refactoring/cleanup
fix up test to test NIO issue
Add font handling to JRobin, implementing DEFAULT, TITLE, AXIS, UNIT, LEGEND, WATERMARK font tags.
Dont use com.sun JPEG classes directly.
update maven dependencies, and plugins
Add NAN-safe addition operator: ADDNAN
Add operator: NE
Add operator: ISINF
Add operator: ATAN
Add operator: ATAN2
Add operator: DEG2RAD
Add operator: RAD2DEG
Add operator: COUNT

Needs work to make sure this only works with CDef's and not SDef's.
fix whitespace
RRDTool allows "MAXIMUM" and "MINIMUM" as VDef (aka SDef) statements, reduce both to MAX or MIN respectively.