[GMSHPolygonTree] Removed method declarations with missing implementation.
[GMSH] Made docu more specific.
Substituted size_t with std::size_t.
[GMSHPolygonTree] Reduced indentation in insertPolyline().
Rename variable to make code more readable.
[PointVec] Documented private method uniqueInsert().
[GMSH] Moved inserting the Polyline to the end of the method.

Before inserting the new polyline, there should be some tests performed with the already existing polylines.
[GMSH] Reformating for readability.
[GMSH] Added GMSHPolygonTree::checkIntersectionsSegmentExistingPolylines().
Added test to check if a point is in polygon.
Activate Polyline test.
Added test for GeoLib::lineSegmentIntersect.
[FileIO] GMSHInterface::writeGMSHInputFile() Move centroid to origin.
[GMSH] Included AnalyticalGeometry.h into GMSHPolygonTree.
[GeoLib] Check if two 3d vectors are parallel.
[MathLib] No constructor for 3 values -> need initializer list.
[GeoLib] Tests for line seg. intersection implementation.
[GeoLib] Changed check of line seg. intersection.