Make ESCLocation is_start_location work (#421)

Introducing BYPASS_LAST_ROOM global to allow changing scene without considering the previous room
Fixes godot-escoria/escoria-issues#40

game/rooms/room13/room13.tscn

@@ -32,8 +32,7 @@ camera_limits = [ Rect2( 0, 0, 1289, 555 ) ]
 margin_right = 92.0
 margin_bottom = 21.0
 custom_fonts/font = ExtResource( 3 )
-text = "ROOM 12
-"
+text = "ROOM 13"
 __meta__ = {
 "_edit_use_anchors_": false
 }