Set config entirely via UI

[ManiMatter]

Related to #337

The current UI allows to set certain configuration items, but not all of them.
Additionally, the "basic" configuration set either via config file or docker is still required.

It would be great if

1. All configuration settings (for instance, per-instance level settings, or per-job level parameters) could be set via UI
2. This could be an additional way to set config (without the need of user configuring yaml)
3. user could export the config as yaml as backup and re-import to restore (or use as config.yaml)