[GeoLib] SimolePolygonTree: docu + style.
[GeoLib] Test for createPolygonTrees().
[GeoLib] Fix bug in createPolygonTrees().
[GeoLib] SimplePolygonTree: node polygon is not deleted in destructor.
[GeoLib] SimplePolygonTree::insertSimplePolygonTree(): Use existing, correct working code.
[GeoLib] Improved readability of createPolygonTrees().
[GeoLib] SimplePolygonTree: Documentation.
[GeoLib] createPolygonTrees(): Fix C++11 issue.

std::list::erase pre C++11 implementation does not take a const iterator. This commit can be reverted if Travis uses a newer version of gcc.
[GeoLib] Restructured and fix bug in isPointInTriangle code.

Impl. a new algorithm for checking if a point is within a triangle and removed old sources for this task.
[GeoLib::Triangle] Using existing code for containsPoint().
[GeoLib] Tests for isPointInTriangle().
[GeoLib] getOrientedTriArea() -> calcTriangleArea().

Renamed and slightly modified algorithm to make it more readable.
[MeshLib/NumLib] MathLib::calcTriangleArea() -> GeoLib::calcTriangleArea().
[MathLib] Remove twice implemented functionality.
[GeoLib] Documentation.
[GeoLib] Impl. of computeAndInsertAllIntersectionPoints().

Conflicts:
	GeoLib/AnalyticalGeometry.cpp
[GeoLib] Test for GeoLib::computeAndInsertAllIntersectionPoints().
[GeoLib] Polygon test: isPolylineInPolygon().
[GeoLib::Polygon] getAllIntersectionPoints().
[GeoLib::Polygon] Impl. of containsSegment().

Method will be used later on to check if a polyline is within the polygon.