Add the structures ILU0Info() and IC0Info() for the preconditioners

[amontoison]

The internal structure that contains the info during the computation of the preconditioner was not destroyed if a null pivot was encountered.
For CSC / CSR formats, I added structures such that we don't take care of that.
For BSR format, I destroy the structure if a null pivot is encountered, I didn't added structures because we don't use often this format...

[maleadt]

I wonder if we should introduce syntax for this, that would allow for automatic scoped destruction (a la defer) instead of relying on the garbage collector. Maybe even just using Defer.jl? Could be done in a later PR.

For BSR format, I destroy the structure if a null pivot is encountered, I didn't added structures because we don't use often this format...

I'd prefer if we act consistently for all cases, if only to make it easier to refactor this code if e.g. switching to a Defer.jl-like mechanism.