[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.
Merge pull request #413 from TomFischer/ReworkSimplePolygonTree

Rework class SimplePolygonTree in GeoLib