Add HTMLElement methods needed by purescript-angular

I'm working on updating purescript-angular to use this module rather than its own DOM interface.  It has an example that requires focus, so I added click and blur as well.

These three methods are on `HTMLElement`, not `Element` so I didn't add them to the class, but I'm not entirely clear how type inheritance is intended to be represented in this module.  For example, the `Document` class exposes `body` which is really on `HTMLDocument`.  If the three added calls should instead just be put on `Element` directly, or a new class made for them, let me know.

Also included are minor other updates.