QR code behind button and faster modal loading

[LukeLambert]

I think placing the QR codes behind a button is important for a few reasons:

• They contain private keys, so there are security implications for having them always visible.
• When multiple codes are displayed on a page at once, it's easy to scan the wrong one.
• At certain screen sizes, they broke the layout and appeared distorted.

I also made it so that content for the modal begins loading sooner (when the button is clicked rather than once the modal has finished animating).

[ngoduykhanh]

Thanks @LukeLambert , this change makes sense to me.
If we remove showing the QR by default, there are more spaces in the panels. I will have follow-up PRs to make the UI looks better.