WIP: Homescreen grouping (v2)

Everything is in a group, dividers act as group separators.

Working:
- Rearranging groups
- Expanding/collapsing groups
- Saving/restoring collapsed state(*?)
- Transitions*

TODO:
- Add moving gripper/indicator
- Creating new groups between groups
- Editable group names
- General polish and optimisation

* Buggy/slow