enhance Quicksilver version checking

implement `minHostVersion` and `maxHostVersion`

As discussed on the list.

I’ve already put a version of the Cube interface out that advertises its lack of support beyond 1.1.3. It’s a little messy, since the update system prevents you from *seeing* that update if you’re already on 1.2.0. But those people have surely discovered by now that the Cube crashes QS. People still on 1.1.3 should get the update.

We need to make a small tweak on the remote side for the update system. When it’s returning a list of plug-ins that support the current version, it will still list the plug-in if `maxHostVersion` is the current version + 1. So `maxHostVersion` is acting like “minimum unsupported version” instead of “maximum supported version”. I think. Basically, I had to add 1 to what was in the database (16391 → 16392) to get the right behavior. :-)