Add QR Code generation

[neocotic]

Add support to display a QR Code for the contents copied to the clipboard in the notification popup. However, this feature should be optional and disabled by default.

Care should be taken to ensure the notification doesn't get too cluttered as the social network buttons added for #12 may also be displayed.

Since a pure JavaScript QR Code generator may be hard to create or find my own server-side generator will be used in the meantime but this should be tested to ensure best performance and lowest load on the server as well as what would happen should the data be too long for a GET request.

[neocotic]

Take a look at using jsqrencode along with to achieve a pure JavaScript QR Code generator.

[neocotic]

I've reworked jsqrencode so that it's cleaner and easier to use. Due to the extensive work involved I've decided to host my own fork under the new name qrcode.js. This will be used by this extension in a format similar to the following;

document.body.appendChild(QRCode.generateImage({
    level: utils.get('qrEccLevel'), // 'L', 'M', 'Q', 'H'
    size: utils.get('qrSize'), // 1 - 10
    value: '' // will need some way of getting copied value (easily done but needs to be managed)
}));

Some new options will need to be added to for specifying these QR settings as well as enabling/disabled QR code display entirely.

[neocotic]

Notification screenshot will need to be updated to display QR code. Also, the template help will also require updating to include the new Option Values.

[neocotic]

Context menus are disabled within notifications so the user will not be able to save the QR code image. Also, the window.location = img.src workaround didn't work.

Due to this I regrettably have no choice but to drop these changes.