Replace Certificate VC with a web-based one on certificate-web-component

[bedinotti]

This will enable all 3 of our environments: iOS, Android, and web, to render exactly the same. It will also allow us to add support for various customizations without reimplementing the same rendering code in all 3 places.

[bedinotti]

I did some work on this, but got blocked. We can't host a file locally and have it request cross-domain resources. https://groups.google.com/forum/#!topic/polymer-dev/K50FqO4R_TY

So our options are:

1. Rewrite blockchain-certificate web component to remove its dependency on some Google Polymer web components
2. Provide a hosted website which would allow cross-domain requests (although the user would have to have internet access to view a certificate)
3. Fire up a local webserver on-device to serve local files as if they were coming from the internet. Apparently, this is something that Cordova does, as mentioned in that forum.
4. Maintain our iOS implementation separate from the web component.

4 is the de-facto choice.