Various fixes and new features

Single chests (Double chests don't work and will notify users if they try to use them)
Bed spawns moving with the ship
Optional per-craft static water levels
Configurable Hovercraft with various customization options (from mwkaicz)
Gravity (from mwkaicz)
Crafts that don't move players/entities (from mwkaicz)

And several misc bug fixes including:
   Fixed a null pointer error when torpedoes explode
   Missing localisation will no longer crash the plugin
   The plugin notifies the console when no .craft files are found