New get/share tabs, button improvements, small UI cleanups

* Add get/share tabs to the UI
* Change permission/start/stop/etc buttons in instance.html to use paper-button styling (more styling coming soon)
* Add uProxy title
* Remove uproxy-button element, these can just be clickable div's, regular buttons or paper-buttons
* Remove uproxy-toolbar, this is easier to style as a div in root.html