Improve automatic experience spend
Improve automatic experience spend

- Don't track non-finite spends
- Allow spending and unspending
- Say which value a trait moved to

gnu-lorien/yorick,gnu-lorien/yorick,gnu-lorien/twistedvines,gnu-lorien/yorick,gnu-lorien/twistedvines,gnu-lorien/yorick,gnu-lorien/twistedvines