Add support for uProxy local FAQ/info page.

Ran grunt test.

The uproxy-faq-link Polymer element will create a link to a local FAQ. The FAQ is opened in a new tab and can be configured to jump to a specific question.
For now, the element is a button, but it can also just be a link. 

Note: I have not tested if this works in Firefox. The content of the FAQ page still needs to be added.