Update input documentation

engine/input/Accelerometer.h

@@ -33,6 +33,8 @@ namespace crown
 {
 
 /// Interface for accessing accelerometer input device.
+///
+/// @ingroup Input
 struct Accelerometer
 {
 	//-----------------------------------------------------------------------------

engine/input/KeyCode.h

@@ -30,6 +30,8 @@ namespace crown
 {
 
 /// Uniquely identifies a button on the keyboard.
+///
+/// @ingroup Input
 struct KeyboardButton
 {
 	enum Enum

engine/input/Keyboard.h

@@ -34,7 +34,11 @@ OTHER DEALINGS IN THE SOFTWARE.
 namespace crown
 {
 
+/// @defgroup Input Input
+
 /// Enumerates modifier keys.
+///
+/// @ingroup Input
 struct ModifierButton
 {
 	enum Enum
@@ -46,6 +50,8 @@ struct ModifierButton
 };
 
 /// Interface for accessing keyboard input device.
+///
+/// @ingroup Input
 struct Keyboard
 {
 	Keyboard()
@@ -58,7 +64,7 @@ struct Keyboard
 	/// Returns whether the specified @a modifier is pressed.
 	/// @note
 	/// A modifier is a special key that modifies the normal action
-	/// of another key when the two are pressed in combination. (Thanks wikipedia.)
+	/// of another key when the two are pressed in combination.
 	/// @note
 	/// Crown currently supports three different modifier keys: Shift, Ctrl and Alt.
 	bool modifier_pressed(ModifierButton::Enum modifier) const

engine/input/Mouse.h

@@ -34,6 +34,8 @@ namespace crown
 {
 
 /// Enumerates mouse buttons.
+///
+/// @ingroup Input
 struct MouseButton
 {
 	enum Enum
@@ -47,6 +49,8 @@ struct MouseButton
 };
 
 /// Interface for accessing mouse input device.
+///
+/// @ingroup Input
 class Mouse
 {
 public:

engine/input/Touch.h

@@ -32,9 +32,14 @@ OTHER DEALINGS IN THE SOFTWARE.
 namespace crown
 {
 
+/// Maximum number of pointers supported by Touch.
+///
+/// @ingroup Input
 const uint32_t MAX_POINTER_IDS = 4;
 
 /// Interface for accessing mouse input device.
+///
+/// @ingroup Input
 class Touch
 {
 public: