sound volumes are now read from and saved to config.rc + bugfix

- fixed calling of IMGUIClear() when the view state changed (was previously
	called only when the game state changed)

engine/doc/Mainpage.h

@@ -72,7 +72,6 @@
  * todos within the code have a look at the \ref todo.
  *
  * \todo [high] Create a simple racing or asteroids game
- * \todo [high] Enable saving of music and effects volume
  * \todo [med] Use shared_ptr instead of raw pointers for the Entities
  * \todo [med] Clear all references of EntityVisualState and EntityGameState
  * \todo [med] Clarify functionalities of CreateEntity, KillEntity, RegisterEntity, UnregisterEntity (which frees memory, which does only change the state of the Model?)
@@ -88,9 +87,10 @@
  * Engine::Module::Init()
  *
  * Done:
+ * \todo [high] (28-11-2010) Enable saving of music and effects volume
  * \todo [high] (28-11-2010) Allow transitions when player dies
-* \todo [high] (11-09-2010) Since introduction of the IMGUI pressing 'space' in the menu crashes the game
-* - [high] In Physics remove dependancy on the Model to pass on collision
+ * \todo [high] (11-09-2010) Since introduction of the IMGUI pressing 'space' in the menu crashes the game
+ * - [high] In Physics remove dependancy on the Model to pass on collision
  *   events
  * - [high] Fix Physics bug when two actors collide actively (i.e. velocity
  *   towards each other)