Merge branch '176-add-drawable-line' into 'master'

Resolve "Add drawable line"

Closes #176

See merge request grp-fidentis/analyst2!185

GUI/src/main/java/cz/fidentis/analyst/scene/DrawableLine.java

+package cz.fidentis.analyst.scene;
+
+import com.jogamp.opengl.GL2;
+import javax.vecmath.Point3d;
+
+/**
+ * A line to be shown in the scene, e.g., to show a ray.
+ * 
+ * @author Radek Oslejsek
+ */
+public class DrawableLine extends Drawable {
+    
+    private final Point3d startPoint;
+    private final Point3d endPoint;
+    
+    /**
+     * Constructor.
+     * 
+     * @param start Start point
+     * @param end  End point
+     */
+    public DrawableLine(Point3d start, Point3d end) {
+        this.startPoint = start;
+        this.endPoint = end;
+    }
+
+    @Override
+    protected void renderObject(GL2 gl) {
+        gl.glBegin(GL2.GL_LINES);
+        gl.glVertex3d(startPoint.x, startPoint.y, startPoint.z);
+        gl.glVertex3d(endPoint.x, endPoint.y, endPoint.z);
+        gl.glEnd();
+    }
+    
+    
+}