-removed UpdateBySystems version switch (it's now default behaviour)

-beginRegister() and endRegister() was added (every register functions must be called between this calls, update calls can't be called there)
-SystemCallers and Systems dependecies is rebuild always in endRegister();
-beginRegister() clear all SystemCallers and Systems dependencies
-possibility to get System ID and execution state
-JobGroup has now pointer to it's parent (SystemCaller)
-SystemCaller clean up destructor

source/ecs/system.d

@@ -45,10 +45,28 @@ struct System
         return m_priority;
     }
 
+    /************************************************************************************************************************
+    *Get system priority.
+    */
+    export bool execute()
+    {
+        return m_execute;
+    }
+
+    /************************************************************************************************************************
+    *Get system priority.
+    */
+    export ushort id()
+    {
+        return m_id;
+    }
+
 package:
 
     ///should system be executed in current update?
-    bool execute = true;
+    bool m_execute = true;
+    ///system id
+    ushort m_id;
 
     ///should system update and catch events?
     bool m_enabled = false;