remove no-tiling implementation
fix status update with cross-hair information (was lost during tiling implementation)
rename PlayViewIntersection to BoardViewIntersection
rename PlayViewMetrics to BoardViewMetrics
rename PlayViewModel to BoardViewModel
replace all references to "Play view" by something more appropriate
rename PlayViewActionSheetController to GameActionsActionSheetController
BoardViewMetrics refactoring, part 5: hardcode more static drawing properties

even more static drawing properties (this time related to scoring) are
now hardcoded in BoardViewMetrics, instead of storing them in the user
defaults.

cf. "refactoring part 4" commit dfb61da26349402e22622f676a2b3b08a583727d
remove unnecessary #imports