add a copy/paste chat sample and some re-shuffling of the other apps

Summary:

* replace `chat2` with a clone of Matt's copy/paste sample from `uproxy-networking`
* `freedomchat-chromeapp` really didn't need to be a Chrome app -- make it a web page
* rename `freedomchat-webpage` -> `freedom-chat-webpage`
Ditto for handleSignalMessage, actually.