-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

dub.json

@@ -10,6 +10,9 @@
 	"dflags-posix-ldc": [
 		"-defaultlib=phobos2-ldc,druntime-ldc"
 	],
+	"versions": [
+		"InputStruct"
+	],
 	"configurations" : [
 		{
 			"name" : "library",