Added evasion buff

- Fixed class cast exception in EntityChu code
- Added EVADE_UP and EVADE_DOWN buffs
- Heavy and Pegasus boots now use these buffs when worn
- Piece of Power also grants evadeUp boost
- Dodge includes these buffs in dodge chance calculation
- removed hard-coded references to boots in Dodge
- added shortcut methods for buffs to ZSSEntityInfo
- cleaned up combat event code