The first implementation was way too complicated and prone to bugs.
This is much more simple flexible; first off, std::function is now used
instead of a raw function pointer, so lambdas and binds are fair game
which is great for scripting. Second, callbacks for all stacks are
executed. It is up to the callback target to ensure correct behavior.
Get rid of `iConditionBitFlag` in favor of a system of individual buff
objects that get composited to a bitflag on-the-fly.
Buff objects can have callbacks for application, expiration, and tick,
making them pretty flexible. Scripting languages can eventually use
these for custom behavior, too.
TODO:
- Get rid of bitflag in BaseNPC
- Apply buffs from passive nano powers
- Apply buffs from active nano powers
- Move eggs to new system
- ???
