Document stability for olx properties

[tschaub]

The stability level will be used to determine what can change between minor releases.

This adds a ton more "experimental" labels to the doc. The next step is to mark more olx properties as stable (see #2578).

[elemoine]

Thanks! Please merge.

[elemoine]

I want to start marking options as stable, so I'm going to merge this PR myself. I hope that's ok to everyone.

[elemoine]

So, as I understand it we need to have @api annotation for the @tydedef's in olx.js. But it makes no difference whether stable or experimental is used for the @typedef. @api just says "I want this type to show up in the documentation. The stability level is indicated for each option, and there's no stability level for the options object itself. I hope my understanding is correct.

[tschaub]

@elemoine that's correct. I couldn't think of a good meaning for the stability level for the @typedef - since we want the ability to mark each property individually. I'll write up a doc for this after a couple more doc changes.