Adding a few small improvements based on feedback.

Changelog:
- Increased the Max FPS from 120 -> 240
- Max FPS can be set to 0 to make it uncapped
- Added the research button to the game over screen
- The range indicator for turrets is now independent of game speed.
- The research menu now must be visited once after the tutorial is completed.

Thanks for all the feedback so far.
Have fun!