Switch to pkg based installer for OSX

And use the same paths, etc as FoundationDB.

The dependency checks are as good as I could get them. They should tell you if you don't have (or have an incompatible) version of Java or FoundationDB-clients. Bundling the latter may be what we do in the future, but bundling the former isn't very clean. The Java installer is distributed as a pkg but with an, unfortunately, not trivial Distribution file.

We should be alright between the new docs, information on the Read Me pane, and the relatively clear error message if one is missing.