Fix transform bugs

* Fixes creature powers being saved to the save file.
* Fixes temporary transformations being saved as if they were permanent.
* Fixes a crash caused by trying to copy Effects between the player and the
transformed creature. This involved adding an overloaded '=' operator to
EffectManager and executing clearEffects() when transforming. This means that
hero effects aren't saved for when they untransform.
* Fixes item bonuses to base stats (Phys/Ment/Off/Def) not being applied when
untransforming.
Fix crash when exiting while transformed

This makes sure we run decrease the animation count based on the hero's
currently transformed state when decontructing the Avatar class.

Also, the ability to manually untransform is now saved to the player's
save file.
Implement proper overloading of EffectManager's assignment operator

This fixes some compiler warnings. It also allows us to preserve the
hero's effects while they are transformed and reapply them when they
untransform.
Merge pull request #348 from dorkster/transform

Fix transform bugs