Firefox App Install

This actually works pretty well as a [firefox web app](https://marketplace.firefox.com/developers/), I put a button on the about page which which allows people to install it, it only shows up if they're using a browser that supports it, which is the beta version of firefox on android and desktop. 

I also made a few other touch ups in the app manifest
* New set of icons in all of the supported sizes
* The icons (obv)
* Force it to portrait orientation EDIT, decided against this one after looking at the screen shots
* Added a version number .

I'd suggest you really should [submit it](https://developer.mozilla.org/en-US/docs/Apps/Submitting_an_app) to Mozilla to put into their app store, they are really looking for more apps.