Gets the norms of each column of a sparse or dense matrix.
PetscErrorCode MatGetColumnNorms(Mat A,NormType type,PetscReal norms)
|A ||- the matrix
|type ||- NORM_2, NORM_1 or NORM_INFINITY
|norms ||- an array as large as the TOTAL number of columns in the matrix
Each process has ALL the column norms after the call. Because of the way this is computed each process gets all the values,
if each process wants only some of the values it should extract the ones it wants from the array.