Made static method a member method of class Polyline.
Changed implementation of Polyline::isPointIDInPolyline().

Method is implemented employing stl functionality to find ID of point in the point id vector.
Made static method Polyline::pointsAreIdentival() a normal function.
Added tests for class Polyline and fixed an issue in Polyline::isClosed().
Using Polyline::getPoint() instead of Polyline::operator()[] to access points.
Removed operator()[] from class Polyline since it is not self-explanatory.
Added tests for Polyline::insert() and Polyline::remove().
Corrected Polyline::insert() and Polyline::remove().