add path to find binary as configuration option

When the script is run on Solaris, it fails because the Solaris version of `find` doesn't support the -maxdepth option.

The GNU `find` is installed by default and called `gfind`, so I added a variable to the configuration file and use that variable instead of `find` in the script. Since the other defaults assume you're running Linux, I used `/usr/bin/find` as the default path.

Another option would be to do some platform detection and pick the right find automatically, but I thought this would be more straightforward.