Further reorganising of opm-core.

Deleted some unused code (or moved to opm-porsol), moved all code dealing with
time-of-flight to opm/core/tof, moved code for implicit transport solver to
opm/core/transport/implicit, spu_[im|ex]plicit.[ch] to opm/core/transport/minimal.

opm/core/tof/DGBasis.cpp

@@ -17,7 +17,7 @@
   along with OPM.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#include <opm/core/transport/reorder/DGBasis.hpp>
+#include <opm/core/tof/DGBasis.hpp>
 #include <opm/core/grid.h>
 #include <opm/core/utility/ErrorMacros.hpp>
 #include <numeric>

opm/core/tof/TofDiscGalReorder.cpp

@@ -19,8 +19,8 @@
 
 #include <opm/core/grid/CellQuadrature.hpp>
 #include <opm/core/grid/FaceQuadrature.hpp>
-#include <opm/core/transport/reorder/TofDiscGalReorder.hpp>
-#include <opm/core/transport/reorder/DGBasis.hpp>
+#include <opm/core/tof/TofDiscGalReorder.hpp>
+#include <opm/core/tof/DGBasis.hpp>
 #include <opm/core/grid.h>
 #include <opm/core/utility/ErrorMacros.hpp>
 #include <opm/core/utility/VelocityInterpolation.hpp>

opm/core/tof/TofReorder.cpp

@@ -17,7 +17,7 @@
   along with OPM.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#include <opm/core/transport/reorder/TofReorder.hpp>
+#include <opm/core/tof/TofReorder.hpp>
 #include <opm/core/grid.h>
 #include <opm/core/utility/ErrorMacros.hpp>
 #include <algorithm>