Track session data

[viddie]

Track a bunch of data session-wise, instead of just totals. This requires:

• [x] Change current system of tracking golden runs to something that's actually serializable with chapter stats
• [x] Add a SessionStarted field to chapter stats
• [x] On first entry of the session into a chapter, call a special method to create old session data. Session data includes
  • [x] SessionStarted
  • [x] Total Golden Deaths
  • [x] Total Success Rate
  • [x] Golden Run Distances of the session
• [x] After that, reset the session specific data (SessionStarted and Golden Run Distances)
• [x] Check separation of path/stats, and loading of those when changing chapter, to avoid conflicts