Merge pull request #25 from ElizabethHudnott/Improve-type-casting,-type-testing,-etc

Moved functions for manipulating types into a new file and revised int()...
Cleanup plugins.js
Remove es5 getter/setter usage in eden.js/plugins.js.

The "internals" object and helper didn't seem to be used enough to justify
having another thing to know about. For now I've removed them and just used
`root.lookup` as we do that everywhere else.
Reduce duplication in plugins.js and docs.
Move plugins/views initialization into Eden constructor.
Fix typos.
Rename active_dialogs to activeDialogs.

It's not massively important, but my aim is to not use underscores in
JS identifiers eventually.
Clean up button.jse.
Update 2ball model for newer js-eden quirks.