Interfaces for matrix generator

[mcopik]

Creating and filling four types of matrices:

• general
• self_adjoint
• triangular, Hessenberg
• banded, diagonal, tridiagonal

For libraries:

• blaze
• Eigen
• Armadillo
• MTL4
• plain C array for BLAS calls

[mcopik]

Necessary for #6

[mcopik]

Redefine shape by adding tridiagonal and diagonal as aliases for banded. Also Hessenberg matrices for triangular.