Demo update

-added 'dot' function to vector math
-fixed Circle tool rendering
-fixed some potentiall memory leaks
-added 'collision' module which now separates ShootGrid from SpaceInvaders demo
-separate some systems from demos to 'basic' module to better demos functionality sharing
-slow down snake
-added new graphics
-BrickBreaker demo now works (without blocks breaking and with bugged collision detection)

-some bug fixes

demos/source/gui/system.d

@@ -5,7 +5,8 @@ import bubel.ecs.system;
 struct SystemGUI
 {
     const (char)* name;
-    System* system;
+    //System* system;
+    ushort id;
 
     bool enabled = true;
 }