1. Started Changes file

2. Added load/cmd_cache.pl to clear cmd cache shortcuts (use this if cluster.pl
get confused about where it is getting its commands from eg if you have
removed a file from local_cmd 'cos you want to go back to standard one)
3. Fixed bull handling at least to the extent that it stores them and
doesn't mess up the normal directory handling.
4. Fixed the unset/debug command so that it actually does the job!
5. Removed the middle line 'written in perl for unix' from show/version.pl