Folder structure for sequence and regimen lists


Some other technicals:

- Search function should also search folder names
- Folders without any matching items should not be shown in search results
- When searching, folders should be opened to display the matching items
- Folder open/closed state should be reset upon page reload, but maintained during an app session
- Folders can be nested up to... 3 levels deep?
- Folders can only be deleted if empty
- All items in the list have a user-customizable ordering
- New folders and new sequences are added to the bottom of the list