Added LOG command.  Logs to a file on the archive volume but only if the
archive 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.
Merge branch 'master' of https://github.com/BGog/KOS into BGog-master
changed syntax, switched code to use existing abstractions