Added camera!

- Can be translated locally or moved to a point in the world
 - Rotates locally around local x- and z-axis and around global y-axis.

Added key checks to test camera movement.

Added Quaternions (Inherits from CoordinatesVector<double,4>) with a view to handling the camera orientation.

Added equality operators for CoordinatesVectors.

Removed slow `glutGet()` calls.
Added custom reshape callback as we now store the window parameters to avoid some `glutGet()` calls.

Renamed `KeyStateManager` to `InputStatus` as it handles more than key states now.

Mouse movement callback now captures the cursor, handles its re-centering and when the cursor enters the window far away from its last position.

TODO : Consider limiting rotations for the camera (Prevents flipping the head around)

src/Camera.h

@@ -0,0 +1,44 @@
+//
+// Created by trotfunky on 19/10/2019.
+//
+
+#ifndef TESTS_OPENGL_CAMERA_H
+#define TESTS_OPENGL_CAMERA_H
+
+#include <cmath>
+#include <GL/glu.h>
+
+#include "Quaternion.h"
+#include "Vectors.h"
+
+class Camera {
+public:
+    Camera(const Vec3d& eye_pos,const Vec3d& look_direction,const Vec3d& up_vector);
+
+    /// Translates the camera relative to its current position and look direction.
+    /// \param translation Translation where x is pointing in the direction of vision.
+    void translate(const Vec3d& translation);
+    /// Rotates the gaze around its local x and z but around global y, relatively to the current orientation.
+    /// This is to provide a coherent movement in regards to mouse movement.
+    /// \param rotation Angles are radians to rotate about each axis.
+    void rotate(const Vec3d& rotation);
+
+    /// Calls the gluLookAt function for the camera.
+    void look();
+
+    void set_position(const Vec3d& eye_pos);
+private:
+    Vec3d eye;
+    Vec3d gaze;
+    Vec3d gaze_up;
+
+    /// Quaternion from the world coordinates to the local coordinates
+    Quaternion rotation_quaternion;
+
+    /// Compute rotation quaternion from the global coordinates to the local coordinates.
+    /// As per https://math.stackexchange.com/questions/2122668/calculate-orientation-quaternion-given-two-axes-of-a-coordinate-system
+    void compute_base_change();
+};
+
+
+#endif //TESTS_OPENGL_CAMERA_H