FIxed GDC compilation (basic betterC WIP) and some improvements

-fixed issue with adding/removing entities inside events handling
-fixed EntityMeta.getComponent() (added check if component_id is valid)
-added function hasComponent to entity to check if component exists

source/bubel/ecs/std.d

@@ -113,6 +113,14 @@ else version(D_BetterC)
         alloca_pos += length;
         return ret;
     }
+
+    version(GNU)
+    {
+        extern(C) void __gdc_personality_v0()
+        {
+
+        }
+    }
 }
 else 
 {