Consider replacing ace editor with monaco

[meisterT]

Monaco (https://microsoft.github.io/monaco-editor/) is more feature rich, in particular supports nice diff views (side by side etc).

We started looking into this because the current way we handle diff views for edit/resubmit (via https://github.com/sebastianbergmann/diff) does not support line ending changes very well.

This will then also make it easier to allow embedding an editor in the team interface.