Slot finder has too many panels

[tdicks]

The slot finder currently has the following panel hierarchy:

• Session
  • Set
    • Songs & Slots
      • Song
        • Slot pips

This UI has a lot of boxes and is a little too busy compared to other parts of the app. Consider how this could be improved or made more consistent. The Practice Plan page uses:

• Set
  • Song
    • Slot pips

A similar approach to this could work if the set panel had the jam session, or if sets were organised by jam session headings.