- Add environment variable to override defaults
- Make serial number postfix consistent across dirs and files
- Add -h help and usage screen

Doc Notes
---------

- Test mode has no effect on -d which always works
- If -d is effective immediately upon reading command line so
  you can clean multiple graveyards with:

   /trm.sh -g ./foo -d -g ./baz -d

- Note difference between -vd and -dv