Make more use of jQuery

I’ve decided a couple of things:
1. If jQuery provides a method which solves your problem don’t write it
yourself
2. Creating new elements is done using the HtmlEngine
3. EVERY node given to a method and returned by a method should be a
jQuery element
4. I’ve created a jQuery-based wrapper around the selection which
enables us to use jQuery elements instead of nodes and simplifies a lot
of things