Move jQuery-specific stuff into jquery.htmapl.js

This should be done as part of the transition to building releases with a `Makefile`.

It might also be nice to build a version that includes a minified (and compatible) `modestmaps.js`. E.g.:
- Bundled mm-js: `htmapl-modestmaps.js`
- No mm-js: `htmapl.js`
- jQuery plugin w/bundled mm-js: `jquery.htmapl-modestmaps.js`
- jQuery plugin, no mm-js: `jquery.htmapl.js`
