[UI] `Open in...` instead of individual buttons

[ryanbugden]

I wonder if it might be both space-saving and extensible to consolidate the two Prepolator / Batch buttons into one "Open in..." button that drops down a menu of options. Then we can add a text editor there as well (I will often go back and forth between Sublime and DSE).

Current buttons

• Prepolator
• Batch

Proposed button & submenu

• Open in...
  • Prepolator
  • Batch
  • Sublime (is it possible to auto-detect default code editor?)