Multiple bug-fixes:

1) Correctly truncate/delete files per the FLO instructions.
2) If we can't add a file to the queue, we still need to track it in the
   flo status to know if we can delete the flow file.
3) Don't truncate the first character of a flow line that doesn't have a
   know prefix (is supposed to be a send and don't delete)
4) Fix exception when calling an unconfigured node.
5) Fix error when detecting the session is done in BinkP 1.1 mode.  If BinkIT
   was connecting to itself, and infinite loop would occur with both ends
   continuously sending empty batches.
6) When calling the tx_callback, pass the filename, not the pending_ack entry.

Additional features:
Call fullpath() in the outbound directory so that symlinks used to work around
sbbsecho's lack of 5D support work correctly.
Fix rx/tx_callback documentation.