Context menu operations for ribbon layout management

[robobenklein]

• Close patch
• Close Column
• Split patch:
  • Left
  • Right
  • Up? (do people use this, is there a reason?)
  • Down
• Move column or patch: (swapping, only displayed when possible? e.g. at top/bottom/left/right edges)
  • column right/left
  • patch up/down
• New:
  • patch above/below
  • column left/right

I realize nobody ever actually used "split patch up" in all my testing... maybe just remove it? It's basically the same result as down.