Make the Fuseki formula more Homebrew-idiomatic

This is a bit of extra work on top of @njh's pull request (https://github.com/mxcl/homebrew/pull/21762) which @adamv requested before merging it. Because @njh's fork was merged into mcxl/homebrew before my fork was merged into @njh's, these changes never made it into homebrew/master.

The key Homebrew-related changes are:

* Explicitly list all files to install rather than globbing
* Install binary files into libexec/ and then symlink them, rather than installing the binaries directly

I figure it may be impossible to merge these automatically now so I've created a fresh fork of mxcl/homebrew and rebased these changes onto the latest master.