support setting spawn point

assets/maps/map1.map

@@ -213,3 +213,9 @@
 ( 3840 832 320 ) ( 3840 832 321 ) ( 3840 833 320 ) TinyTexPack2/Brick/Brick_14_window [ 0 1 0 0 ] [ 0 0 -1 0 ] 0 1 1
 }
 }
+// entity 1
+{
+"classname" "spawn_point"
+"origin" "152 232 -248"
+"scale" "50"
+}