More test cases for disjoint

* Add a few more test cases, some of them related to the recent bug in the Cartesian segment-segment intersection strategy (see PR #175).
* Replace calls to `BOOST_CHECK` by calls to `BOOST_CHECK_MESSAGE`.
So this becomes much more readable too, msg << "G1: " << bg::wkt(geometry1) << ", G2" << bg::wkt(geometry2) << " -> " etc.