Add new Buoyancy script

Sourced:
- http://forum.unity3d.com/threads/buoyancy-script.72974/
- http://forum.unity3d.com/attachments/buoyancy-cs.16416/
Replace ShipBuoyancy with Buoyancy script
Increase size and tweak position of Boat Box Collider

This makes it a better fit for collisions and buoyancy.
Move the position of the skybox in Prefab

Computer generated nonsense.
Replace ShipBuoyancy script within Player prefab

Updates the Buoyancy script inside Player prefab.
Update BoatPrototype scene with updated prefab
Merge branch 'feature/turnBoatIntoWindDirection'

* feature/turnBoatIntoWindDirection:
  Update BoatPrototype scene with updated prefab
  Replace ShipBuoyancy script within Player prefab
  Move the position of the skybox in Prefab
  Increase size and tweak position of Boat Box Collider
  Replace ShipBuoyancy with Buoyancy script
  Add new Buoyancy script
Add controls for mouse input (for testing purposes)