Added LOG command.  Logs to a file on the archive volume but only if the volume is within range.

Otherwise the message is lost to space.

Works similarly to PRINT with the addition of a log filename argument.
  LOG mylog "Hello Eve."
Would append "Hello Eve." to the end of the mylog.txt file on the archive
volume.

When out of range, the message is silently dropped.

Note:  At this time I didn't think it was a good ideas to support logging to volumes on the ship as it would quickly eat up space and I need to think about ways to manage that and keep the user experience simple.    Also it is kind of fun to have to deal with KSP being withing range to get your telemetry data from your program.