Added some more comments to 3D algorithm, and fixed a bug that affected some of the degenerate cases.

Replaced global variables by a new hydro_space struct that is part of space. This struct is then passed on to hydro_init_part, and used to initialize the Voronoi cells. For non SHADOWFAX_SPH schemes, this struct is empty. Replaced random_uniform declarations in some unit tests with the tools.h version. Added some more comments to 3D Voronoi code; it is now almost completely documented (meaning I almost completely understand it now).

Added a lot of comments to 3D Voronoi algorithm, fixed bug in testVoronoi3D. Disabled expensive checks. Some basic 3D moving mesh tests now work.

Added actual grid test to testVoronoi3D; degenerate case crashes. Started documenting 3D Voronoi algorithm to refresh my memory about how it works.

Fixed bug in low order vertex removal. Moving mesh now seems to work, but there is strange noise in some of the snapshots...

Added some more comments and better debugging output. Moving mesh algorithm sometimes works and sometimes does not...

Started implementing order 1 and 2 vertex removal. Fixed problem with absolute vs relative face midpoints in testVoronoi3D.

Found error in face midpoint calculation. Algorithm now sometimes gets stuck in an endless loop due to wrong geometry...

Added extra check in complicated 3D Voronoi setup. Need to implement order 1 and order 2 vertex collapse routines.

Constructing a 3D voronoi grid now seems to work. Still need to find a way to correctly initialize the box.

Added face calculations and unit test for 3D Voronoi algorithm. Started testing 3D moving mesh, does not work.