[refactor] New buff framework (player implementation)

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
- ???

src/Entities.cpp

@@ -83,6 +83,10 @@ void Egg::enterIntoViewOf(CNSocket *sock) {
     sock->sendPacket(pkt, P_FE2CL_SHINY_ENTER);
 }
 
+sNano* Player::getActiveNano() {
+    return &Nanos[activeNano];
+}
+
 sPCAppearanceData Player::getAppearanceData() {
     sPCAppearanceData data = {};
     data.iID = iID;