Regular matrix functionality is not implemented

[MaxGoryunov]

There are functions for working with sparse matrices in Sparse module, but there are no functions for regular matrices. The list of required functions is the same as for sparse matrices:

• creating an identity matrix
• reading matrix from file
• printing a matrix
• matrix addition/subtraction
• matrix multiplication by a number
• matrix miltiplication by a vector
• matrix multiplication by another matrix
• creating a random normalized orthogonal matrix
• creating a diagonal matrix from a given vector