Allow Carbon Wallet to run as a Chrome Packaged App

This update will let Carbon Wallet be run as a Chrome Packaged App.

To run it as a packaged app locally without getting it from the Chrome Web Store:

1) Go to "Menu > Tools > Extensions" in Chrome
2) Make sure "Developer mode" is checked at the top
3) Click "Load unpacked extension" at the top
4) Navigate to the carbonwallet.github.io directory and click OK
5) Carbon Wallet will now appear as an option in your App list in Chrome

I have made these changes so that it could become a packaged app:

1) Included a new icon in several sizes under images/icons/.  I don't care if this graphic is changed, it just needs something.

2) Changed the regular js "alert" call (there was only one instance of it) to alertModal instead, which uses Bootstrap's modal feature. alert is not allowed in packaged apps.

3) In extjs/bitcoin/script.js, changed all OP_* vars to reference an object instead of being directly evaluated, because "eval" is not allowed.

4) Link to local copies of Bootstrap and Font-Awesome CSS.  Also added the font/ directory so this could work.

I have already published it to the webstore and it is pending display.  Here's the URL it'll show up at when it's ready:

https://chrome.google.com/webstore/detail/carbon-wallet/oomodnghgnjdmdfhjchencjibneefpah

Ideally I'll just give control of this to the original manager of the Carbon Wallet if they are interested.

Let me know what you think.