Multilevel

[ErnWong]

• [x] Show score at end screen of every level
• [x] Intro story / tutorial should not show again on next level. (Or have new dialog / events)
• [x] Restart button would not show start screen - immediately start and regenerate at the same difficulty
• [x] Pass difficulty parameter to map generation
• [x] @Sabatr is going to increase probability of events based on stats.

Things to change:

• [ ] Increase initial factory / CO2 / temperature ratio.
• [x] Terrain.
• [ ] event frequency.