Add loader to the MIP and results screen

[jstavh]

No description provided.

[robinbb]

Here, I think that "loader" means "spinner" or "loading modal" or some such.

Basically, we want the site's web pages to appear nearly instantly, even if the associated blockchain data takes a few seconds to arrive from the back end. (This delay is likely.) This should be easily possible because the web page itself never includes the data from the back end, which arrives via JSON payload.