refactor(client): Extract form decorators into their own modules.
chore(client): Remove polyfills.js, it is not included anywhere.
Merge pull request #1471 from mozilla/remove-polyfills

chore(client): Remove polyfills.js, it is not included anywhere.
Merge pull request #1454 from mozilla/extract-decorators

refactor(client): Extract form decorators into their own modules.
adding missing copyright header
Merge pull request #1475 from pdehaan/issue-1474-copyright

adding missing copyright header
feat(oauth): message to native flows
Prepare the OAuth completion logic for multiple channels.

* Remove the @vladikoff's FxWebChannel for now to simplify review. I will add this in a separate PR.
* Create a BaseChannel which is the channel interface, base other Channels off of this.
* Extract the current OAuth redirect code into its own channel named RedirectChannel.
* Add helper functions to service-mixin.js to clarify intentions.
* Upon OAuth completion, display a spinner on the available submit button.
* Upon OAuth completion, if no response is received from the channel within 10 seconds, display an error message.
Channels are now ephemeral, no more storing channels on Session. Mock in some OAuth server interactions.

* Bring the channel factory back. Simplify it's API. The only method is `get`, it takes a `window` as a paramter. All other info is taken from Session.
* Use the channel's `send` interface to determine whether it supports OAuth auto-verification.