-added absen components list to system

-added ECS uda attributes
-added InputStruct version switch (gets update() input as structure of arrays)
-initial (WIP) EntitiesData update() input structure compile time parsing

source/ecs/attributes.d

@@ -0,0 +1,4 @@
+module ecs.attributes;
+
+enum optional = "optional";
+enum absen = "absen";