Fix uninitialized variables in Utilities::MPI::MinMaxAvg
Merge pull request #254 from kronbichler/fix_mpi_min_max_avg

Fix uninitialized variables in Utilities::MPI::MinMaxAvg
fixed a bug in set_matrix_mode.

STSetMatMode shall be called only after transformation_data->st
is initialised. Thus, we need to store the desired STMatMode
untill set_context is called from the solver object.
Merge pull request #246 from davydden/set_matrix_mode

fixed a bug in set_matrix_mode.