lots changes:

- renamed scene files
- fixed options back using scene.Prev
- fixed initial zooming (finally)
- fixed reset zoom (key r)
- fixed initial size, now works with state loading as well

TODO.md

@@ -2,16 +2,3 @@
 
 - changing options mid-game has no effect in most cases, even after a restart
 
-- Statefile loading does not work correclty anymore. With larger grids
-  everything  is empty.  With square  grids part  of the  grid is  cut
-  off. Smaller grids load though
-  
-- Also  when loading a state  file, centering doesn't work  anymore, I
-  think the geom calculation is overthrown by the parser func. So, put
-  this calc into its own func and  always call. Or - as stated below -
-  put it onto camera.go and call from Init().
-  
-- Zoom 0 on reset only  works when world<screen.  otherwise zoom would
-  be negative So, on Init() memoize  centered camera position or add a
-  Center() function  to camera.go.  Then on  reset calculate  the zoom
-  level so that the world fits into the screen.