Fixed the refactoring for now?
Simulation validation now runs fine.  Problem was a bug in the actual kernel.pdf!!
Added tests for kde models and kernels.
Added to cad SEPP code.
Started looking at network code - fixed a few errors I had introduced by removing the tag 'linestring'
Added several new KDE models - one-sided in time normal and exponential in time, normal in space.
These *don't* seem to fix the issue when validating with simulated data - was expecting a good match close to t=0 but still a fair way out.  Maybe the best possible solution is a normal kernel that REFLECTS at t=0?  Will be slower!  TODO: give it a go.
TODO: having issues getting this working properly on the Cad data again - why is that?  Seeing very very tight spatial extents.