boat/island/input/communication changes

Major Changes:

* The active screen now passes input handling to each player and then reads any messages the player sends back
* Randomized player colours have been implemented (trust me)
* Boat and Island creation by colour is set in place, but we need the textures (or at least placeholders)
    * For Boats, just name the textures to match the ones listed in Boat.cs and put them in the Boats folder
    * For Islands, just name the textures appropriately, put them in the Islands folder, and add the names of the textures to the appropriate lists in Island.cs.  There is a list of textures for each colour and each time an Island is created, a random entry from that list will be selected.
    * Once all colours have one boat and at least one island texture, uncomment all the lines in Player.cs referring to Boat or Island.
* You can hit Enter or Start on controller to go from Main Menu -> Main Game -> Game Over.  I added a delay so you can't swap quicker than every quarter second (previously it swapped multiple times per keypress).
* The Main Game now draws a nice Wheat-coloured background.  This is for Diego.

See you at lunchtime.