Cleaned up the reflection code a bit

* Renamed 'tag' variable to 'handler'
* Removed addAlias stuff, instead check for matching names with if statements
* Added after_reading function that is called by Reader after reading a complete object. This generalizes Packaged::validate, which is now also called via this mechanism.
* Removed some backwards compatibility with <0.3.0 for templates

src/data/game.hpp

@@ -76,7 +76,7 @@ class Game : public Packaged {
   protected:
   virtual void validate(Version);
   
-  DECLARE_REFLECTION();
+  DECLARE_REFLECTION_OVERRIDE();
 };
 
 inline String type_name(const Game&) {