#8 Add file descriptions to command line switches

[Kurt]

Use description that shows up in built-in compare
tool with the external tools. This will be most
useful when integrated with CVS, since filenames
could be the same, but one file local and one
remote.

The command line switches are different for each
external tool, though. Might have to redesign the
command line helper to ask the user which of the list
of external tools they're using, then give access to
the switches for that tool.