Refactor app state

In #33 we started refactoring the app state to make it easier to introduce new features and reduce tech debt. So far it has been successful in making the state logic more manageable, but there were features that needed to be disabled momentarily until they were refactored into the new approach.

This is a ticket to track the features that need to be reinstated and also the regressions that were introduced in the refactor:

- Features:
- [x] Layers panel
- [x] Batch workflow
- [x] AOI edit
- [x] Retrain tab
- [ ] Refine results tab

- Regressions:
- [ ] Clicking on User Dropdown, "Project New" doesn't redirect to a new project

Please feel free to add items that are not tracked elsewhere.

cc @geohacker @srmsoumya

No files or tests are named. Start by reading issue #33 and reviewing the remaining checklist items: the Refine results tab and the User Dropdown “Project New” redirect; done means those regressions are reinstated and any additional tracked items are resolved.

Written by the indexing model from the issue text.