save the entire game when user views an old board position (fixes #150)

cherry pick e4a7186 from branch 'develop'
fix memory leak in TableViewSliderCell (fixes #155)

cherry pick 3f6087b from branch 'develop'
board position can no longer be changed while "genmove" is executed (fixes #156)

change details:
- PlayMoveCommand is now fully synchronous to prevent any chance of a board position
  change between submitting the "play" and the subsequent "genmove" GTP commands
- controllers that trigger a board position change now check first whether a "genmove"
  command is currently in progress; if they find that this is the case, they silently cancel
  the board position change just as if the user had not triggered the UI element in the
  first place; the assumption here is that the user has triggered the UI element by accident
- NavigationBarController now also performs a "genmove" check when certain bar button
  items trigger, because these items have the same potential weakness as the board
  position change UI elements
disable zombie objects for adhoc and app store distribution

the answer to SO question [1] says that zombie objects are disabled when
the app is archived for app store distribution. I don't know how to verify
this assertion, so I turn the option off to be on the safe side.

[1] http://stackoverflow.com/questions/2190227/how-do-i-set-up-nszombieenabled-in-xcode-4
app no longer crashes after receiving memory warning on iOS 5 (fixes #157)
final tidying up for release 0.11.1
Merge branch 'hotfix-0.11.1' into develop

Conflicts:
	src/command/game/SaveGameCommand.m
	src/play/PlayViewController.m
	src/play/boardposition/BoardPositionToolbarController.m
	src/play/controller/NavigationBarController.h
	src/play/controller/NavigationBarController.m

Resolutions
- SaveGameCommand.m: No change required, this conflict arises because
  of the cherry-picking in cdc50ea; the cherry-picked change is already in
  branch 'develop'
- PlayViewController.m: Changes merged into NavigationBarController.m
  because PlayViewController.m no longer exists (due to earlier extensive
  refactoring in branch 'develop')
- BoardPositionToolbarController.m: Simple merge
- NavigationBarController.h: No change required, the method that was
  eliminated in branch 'hotfix-0.11.1' is already gone in branch 'develop'
- NavigationBarController.m: Simple merge