Mostly bugfix update + empty components support and remove EntityID from Event structure

-empty components now take no memory, so flag components is now far better
-added test for critical bug
-fixed critical bug with adding/removing entities form inside events
-fixed small bug with TestRunner
-improve basic tests
-fixed betterC compilation on DMD
-remove EntityID form Event structure
-added "return" attribute to some functions
-moved some code from Tempalte side to actual implementation
-fixed bug with EntityTemplate copying
-commented out some possibliy unused code
-use code formatter

source/bubel/ecs/attributes.d

@@ -25,4 +25,4 @@ module bubel.ecs.attributes;
 ///Used to mark optional components for system.
 enum optional = "optional";
 ///Used to mark readonly components for system. "const" can be used insted.
-enum readonly = "readonly";
+enum readonly = "readonly";