The geometry and push structure has been reworked to allow eassy adding
new pushers.
Documentation not updated yet.
Baseline for merging Cartesian pushers into one.
In each iteration, number of collisions are calculate as a REAL variable
(collFrac) and stored in each cell. The number of collisions is
calculated as FLOOR(collFrac) and, if it is >1 collisions are computed
as usual. Per each collision calculated, 1.0 is removed from collFrac
Now collisions can have a different time step.
Added species name to output names as it was starting to get confusing
in Gmsh for multiple species.
Output filenames adapted to match any number of iterations.
