WIP: Homescreen grouping (v2)

Everything is in a group, dividers act as group separators.

Working (to a fashion):
- Rearranging groups
- Expanding/collapsing groups
- Creating new groups between groups
- Saving/restoring collapsed state
- Transitions

TODO:
- Editable group names
- General polish and optimisation (pending Gecko bugs)
Yeah, I'm not sure why this deletes, I think I was trying to maintain existing behaviour or something... I'm not keen on using the ternary operator in that way though, I'd rather keep the if block in.