Effects editing - Fix build warnings and other cleanup

- Add @optional postDeserializationEffectFixup to EffectProtocol to fix compiler warnings.
- Remove unused "@property (nonatomic) CCBPEffectHue *effect" from CCBPEffectHue.
- Remove EffectDescription property declarations from CCBPEffect classes that have them.
Not all effect classes declare them (or other members of EffectProtocol) so remove them to
make things consistent.
- Make CCEffectNodeProtocol's NSArray *effects property strong. One header had it as assign
and one didn't specify (making it strong by default).