Implement Circle header, rename all files to use .hpp extension.

include/J3ML/Geometry/Line.hpp

@@ -0,0 +1,24 @@
+#pragma once
+
+
+#include "LineSegment.hpp"
+
+namespace J3ML::Geometry
+{
+    class Line
+    {
+    public:
+        Vector3 Position;  /// Specifies the origin of this line.
+        Vector3 Direction; /// The normalized direction vector of this ray.
+    public:
+        static void
+        ClosestPointLineLine(const Vector3 &v0, const Vector3 &v10, const Vector3 &v2, const Vector3 &v32, float &d,
+                             float &d2);
+
+        Vector3 ClosestPoint(const J3ML::Geometry::LineSegment &other, float &d, float &d2) const;
+
+        Vector3 GetPoint(float d) const;
+
+        Vector3 ClosestPoint(const Vector3 &targetPoint, float &d) const;
+    };
+}