Update layout to add segmented control switch
Add card matching mode property to game model

Matching mode is set to 2 cards when the game is initialised, and then
reset whenever the UISegmentedControl's value changes.
Refactor card flipping to allow for n-card matching modes

- Add SCSCardMatchingMode class to encapsulate the game mode and
  relative match scores
- Update SCSCardMatchingGame to use new matching modes, and to match
  based on the concept of "cards in play"

The new algorithm based on "cards in play" should be able to handle up
to n-card matching modes, instead of being limited to 2- or 3-card
modes.
Update matching algorithm for multiple cards
Merge branch '3-card-match' into develop
Break out of loop if game initialisation fails
Update flip result string to handle more than two cards
Disable mode switching upon flipping a card
Merge branch '3-card-match' into develop
Create tab bar controller and empty scores screen