vector and matrix functions

[jbrezmorf]

dot(a, b)
det(A) - determinent of matrix
norm(v) - l2 norm of vector or matrix
norm(v, exp) - lp norm
norm_max(v) ..
inv(A)
eye(n)
zero(n,m)
diag_mat(vec)
diag(mat)

reduction operations: sum, prod, mean, ...

[jbrezmorf]

Test 'pi' and 'e' constant support.

[jbrezmorf]

test Array::concatenate - current implementation is possibly buggy
parser support for concatenate (not critical)

[jbrezmorf]

In order to avoid the implementation of whole linear algebra, we can use Eigen with a custom scalar type.
Eigen has support for this case

Eigen can be used as a header-only library so we can have it possibly as a submodule.

We possibly have to wrap Eigen operations to allow Python-style broadcasting that is already implemented.