Reduce public API on DOM nodes

[arv]

Right now we expose way too much (due to implementation details)

We should only expose

• model
• modelDelegate
• addBinding
• removeBinding
• bindingText

and maybe

• addValueBinding
• addCheckedBinding

We currently expose

• [x] modelChanged
• [x] modelDelegateChanged
• [x] lazyModelChanged
• [x] lazyModelDelegateChanged
• [x] valueChanged

And HTMLTemplateElement exposes a few more that we want to hide.

[arv]

cc375b2f43508fdebd4cc404c665eb8a138ac42f 3d1eacf7dd0f8cb1089c467d46db82f2be8b5349

[arv]

a9202eacea8d7ebd86280f9b4889618e9b8b156d removes the other ones from HTMLTemplateElement

[arv]

Fixed in ff10f292c85309b9fce4bccdd465bd84d5e80781