Bug 967

Fix bug 967 http://bugs.openmw.org/issues/967

Fix startNewGame assigning an already freed CellStore to the player Ptr supplied to WindowManager. Fixes a crash when equipping lights after starting a new game (bug 967). Side note: The inventory preview's Ptr being assigned a cell at all doesn't make sense, as that is used to determine the light setting which should be the same no matter which cell you're in.