Currently we're fetching compass' instance when the global `refresh-data` message is emitted in the app registry and when the data service connects `data-service-connected`. This is handled by compass-app-stores which has an instance of mongodb-instance-model. This ticket involves moving the handling of those events to `compass-home` and keeping the instance in the state of the component there (where it can be, in later tickets, passed through props to components). We should remove mongodb-instance-model then and keep it as a plain object.

It does look like there are some places that rely on `global.hadronApp.instance` being available, we should continue letting it be so unless we want to address it in this ticket.

Maurizio's gist of moving instance fetching to ts and has a few cleanups also: https://gist.github.com/mcasimir/7f089a2e66018cf12c4cc1e516b08526