Fix bug in creation of neighbour distances of StructuredGrid.
Fix diffusive jump rate calculation for grids other than StructuredGrid. Also fix face rectangle lookup for OctreeGrid.
Expose new Grid, StructuredGrid and OctreeGrid interface, with NextSubvolumeMethod to python. Introduce method to get concentrations from an OctreeGrid.
Fix crash where we did not implement the is_in check correctly for Octree. Add debugging assertions.
Fix compilation error in OctreeGrid.h