Some performance or memory optimizations

Replaced String concat in loops with StringBuilder (performance)
Replaced for with keySet + Map.get() through for with entrySet (perf)
Changed inner classes to static classes, mostly struct like (memory)

src/main/java/appeng/core/api/ApiPart.java

@@ -196,7 +196,7 @@ public class ApiPart implements IPartHelper
 		}
 	}
 
-	class DefaultPackageClassNameRemapper extends Remapper
+	static class DefaultPackageClassNameRemapper extends Remapper
 	{
 
 		public final HashMap<String, String> inputOutput = new HashMap<String, String>();