Aggregation test demo using live covariance server

[abought]

🦑 Depends on: https://github.com/statgen/raremetal.js/pull/8

Purpose

Small tweaks to the aggregation test demo, to support fetching live data from a server.

This includes refactors for a more readable dynamic UI (based on VueJS) and changes to the base schema/datasources.

The example will be completed once updates to raremetal-server are in place.

PAYLOAD DETAILS:

• [x] Key on gene name, or gene id?
• [x] The LD server outputs some masks for genes not shown in our genes track. Why?
• [x] In certain cases, the LD server can return masks / group that contain no variants at all. We need to update the server OR rm.js to deal with this.
  • If neither is feasible, a fallback option would be to lock the plot region to prevent scrolling.

TODO:

• [x] UI refactor to support real metadata/ new fields
• [x] Identify plot region with interesting results
• [x] Add loading indicator
• [x] Handle empty regions (no covariance data)
• [x] Real URLs/covariance requests
• [x] Update raremetal.js documentation to reflect correct field names
• [x] Turn off Vue prod mode + use CDN version of new raremetal release
• [x] Use a "real" LD server url