Debian/Ubuntu init script

It may not be beautiful (especially the `bash --exec` trick) but it is working here.

There are still improvements that could be made, but they might not come soon!

- Should append to logfile rather than clobber it.  Use `>>` in initscript instead of `>`

- But then we should also create and install a logrotate config file.

- Add dates to log messages.

- If it isn't too difficult, also logging the arguments passed to the process when it started could be useful.

- To go even further, if the process in an X app, we could display its window title.

- More configurability: trigger %age, option to trigger only if RAM *and* swap are full.