Unify UI layout

[herzbube]

The app currently has very different UI layouts for the three UI types.

• Smaller iPhone devices that don't support landscape orientation (UITypePhonePortraitOnly)
• Larger iPhone devices that do support landscape orientation (UITypePhone)
• iPad devices that support landscape orientation (UITypePad)

A decision has been reached to unify the layouts of the three UI types as much as possible. These were the main decision drivers:

• The effort to support three different UI layouts has become too much. This became apparent after some prototyping how to display SGF node and move annotations. Each of the three UI type has its own implementation how to display board positions. Since board positions now represent nodes, the changes that are necessary for displaying SGF node and move annotations would have to be made in three different places, proliferating the wild variety and making things even worse in the future. This is not sustainable, so the first unification goal is to have only one way of displaying board position: Using UICollectionView and BoardPositionCollectionViewCell. This means changing UITypePad (get rid of the table view based approach) and UITypePhonePortraitOnly (get rid of the alternative UICollectionView implementation that uses BoardPositionView as the cell type).
• Once the displaying of board positions has been unified, it should be considered to also unify the way how board positions are navigated. Specifically, UITypePad and UITypePhonePortraitOnly currently have hacks that mangle UIToolBar into submission, so if possible these should start to use the custom ButtonBoxController view controller instead of a UIToolbar.
• The layout for UITypePhone looks quite neat in my opinion, but the pain and workarounds it took to implement are pretty horrible, and not everything works 100% the way it should. Plus every time I upgrade to a new iOS version there is a new set of smaller or bigger issues that need to be fixed. Again, I am no longer willing to spend the time to support this, so I am going to switch to an UITabBarController based layout on UITypePhone. The drawback for the user is that in landscape orientation the board will have less vertical space and will therefore become smaller.
• After switching the UITypePhone layout to use UITabBarController, it should be very similar to the UITypePad layout. There is a huge promise that the two layouts can be merged, with only minimal differences between them.
• Layout unification provides a new chance to finally understand and support the extended layout concept introduced way back in iOS 7. This should get rid of various hacks that set edgesForExtendedLayout to UIRectEdgeNone and automaticallyAdjustsScrollViewInsets to NO.

[herzbube]

A consequence of the unification effort is that in Portrait orientation the vertical space available for the board view is now slightly reduced.

For most iPhone devices this is not a problem, because for them the vertical space available is still larger than the screen width, so the screen width remains the limiting dimension for the square board view.

However, for the smallest iPhone devices that the app still supports - the iPhone 5S and the iPhone SE (640 points vertical screen size) - the reduction means that the vertical space available is now less than the screen width, so the vertical space available now becomes the limiting dimension. In practice on the affected iPhone devices for some board sizes coordinate labels and/or move numbers and label markup will no longer show up without zooming in.

[herzbube]

Ready for next release, closing this issue.