Added an IsConnected member function to the InputDevice base class

|SOURCE|
[Common/Game]
* The Gamepad instance has been moved to a member variable
* The Gamepad's connectivity is verified before attempting to obtain the
  gamepad state date
[Common/InputDevice]
* IsConnected returns whether the device is classified as connected to the
  computer
[Common/Gamepad]
* If any of the file descriptors are invalid, the connectivity status is set to
  false
Started work on an input device abstraction layer

|SOURCE|
[Common/Game]
* Added a pointer to an InputManager
* Added a Keyboard instance
* In the main loop, when the escape key is pressed the game exits
[Common/InputDevice]
* Added an enum for keyboard keys
* Added a struct to hold keyboard keys and the key moifier state
[Common/InputManager]
* This is the base class to be derived from for the platform specific
  interfaces
* AddDevice registers the device passed in to either a mouse, keyboard, or
  gamepad (currently only one of each are planned to be supported)
[Common/Keyboard]
* Deriving from the InputDevice class, a keyboard provides an interface to set
  and get the key state
[Common/EGLWindow]
* Removed the ProcessEvents definition from the common source, instead each
  platform defines a specific ProcessEvents member function
[Linux/LinuxInputManager]
* Currently only the keyboard press and release events are handled, all other
  events are put back on the event queue
* MapKeyToChar returns the character of the key
[Linux/LinuxEGLWindow]
* A simple window is no longer created, instead it has been replaced by a
  standard window which also listens for more event types
* ProcessEvents handles any relevant events, those which are not handled are
  put back into the event queue for other event processors to handle
Added more data types

|SOURCE|
[Common/DataTypes]
* Added data types which are immediately useful
Disabled the dialogue box option to use OpenGL | ES 2.0 on Linux

|SOURCE|
[Linux/Game]
* Removed the dialoguebox option to select between an EGL+GLES2 or X11+GL
  instance of the game, as the OpenGL | ES 2.0 version is the primary focus
Started work on the Pandora's keyboard input

|SOURCE|
[Common/InputDevice]
* Changed the GAMEPAD_BUTTON_* constant names to better reflect the Pandora's
  button input
* Added AURA_KEY_* constants to expand the keyboard input to the A-Z
  characters, 0-9, and F1-F12 keys
[Common/Keyboard]
* Added a file descriptor for the keypad on the Pandora
* Removed the Initialise, Terminate, and GetState member funcitons from the
  common source to be platform-specific
[Common/Game]
* Added checks for the window and input manager's memory allocation
* Changed the gamepad quit button to select
[Common/Gamepad]
* Added a table to map code values to button values from the gamepad hardware
* Changed the press/release to use the table for code values to button values
  to set the button states
[Pandora/PandoraInputManager]
* Much like the Linux version, the PandoraInputManager maintains device state,
  though as the functionality is programmed in the device for the Pandora, this
  is largely useless
[Pandora/Game]
* PreInitialise initialises the InputManager instance to be a
  PandoraInputManager instance
[Pandora/Keyboard]
* Added a table to map code values to the key values they represent
* Initialise finds the keypad device for input, if it can't find it an error
  code is returned
* GetState acts much like the Gamepad and uses select to grab whatever state is
  available, returning immediately, then the code values are mapped to keys
  which are kept internally with m_KeyState.Keys