Coarse direct solver for MatrixFree (also block version)

[Michał Wichrowski]

Dear all,

I've wrote a interface for Trilinos direct solver so that it may be used as coarse solver for MG. It assembles the matrix by using N vmults (so this part is very inefficient), so it will only pay off if solver is used multiple times.  I've got also block version. It is possible to extend block to work as an (efficient) direct solver for block matrices. Since we do not have a parallel direct solver for block matrices it might be an useful tool.  

Best,

Michał