for scaling tests, if we don't want to get stuck on I/O things...

Update particle spline classes up to 10

See merge request !12

keep NSVEparticles, since it's a child of NSVE and everything is more
consistent this way

results should (and seem to be) equal within numerical precision (maybe
even binary for good settings).

add ";" after function declarations.

it should work for many many particles now.

there were a few issues with read_parameters, which is now a virtual
function in NSVE.

since we now have the full_code classes, I guess it makes sense to use
the full name for the old version.

assume each checkpoint file should be at least order 1GB, and then check
how much space each checkpoint will require.
this includes both field and particle data.

this means i defined a virtual "step" method, as well as "do_stats" and
"write_checkpoint".
I think this makes it even more clear what job is assigned to which
class.

Feature/longlong particles

See merge request !11

Ensure to find all neighbors processes (especially with width interpolator)

See merge request !10

Add simplified wrapper called `DNS`.
While this will make it slightly more complicated to generate
peculiar custom codes, the experience so far has been that this current
version is quite adequate for our needs.

Most of the code generation is removed from the Python wrapper, and
plain old C++ classes are written for each type of simulation that is to
be run.

Feature/limited particles output

See merge request !9