Unification of boundary conditions into one file.
Some changes to input file for reference cases. This should have been
done in another branch but I wanto to commit to save progress and I
don't want to deal with tswitching branches right now, I'm very busy
watching Futurama.
Now, the solver needs to be an input parameter of the case, to select if
it is for charged or neutral particles.
Resolution of Poisson equation with Dirichlet boundary conditions is
possible. The source vector is the charge density. This resolution is
done in two steps to save computational time:
1. When reading the mesh, the PLU factorization of the K matrix is
computed.
2. In each iteration, the system K*u = f is solved, in which f is the
source vector (charge density) and u is the solution (potential) in
each node.
No case has been added to the repository. This will be done in next
commit.
The 'non-analog' scheme has been commented. It still needs to split
the particle to avoid 'overweight' particles.
