Simplify ShaderManager API

[bitbrain]

It is currently too complicated to configure shaders. Exposing the internal shader via getInternalEffect() is dangerous, since people might not use the decorator effect. Instead, remove the getInternalEffect() method and do this:

public interface Mutator<T> {
   void mutate(T target);
}

And then:

AutoReloadPostprocessorEffect<Blur> effect = shaderManager.createBlur(
   new Mutator<Blur>() {
      @Override
      public void mutate(Blur blur) {
         // mutate blur here
      }
   }
);

Additionally, all effects should have a new method called mutate(Mutator<T> t) which allows setting/changing the internal shader.

This gives us several advantages:

• we always set values on the current effect object
• initialization becomes more clear
• users are forced to use the decorator which avoids potential bugs