linalg: hermitian

[perazz]

Address #883: compute the Hermitian version of a rank-2 matrix.
I agree that having a hermitian helper function is inline with stdlib already offering several others, including is_hermitian.

Fortran uses verbs (transpose), so there is no direct equivalent. I believe another possible name for this function may be just hermite(A), but probably hermitian is more in sync with is_hermitian.

Proposed implementation

• A_h = hermitian(A)

Key facts

• For complex matrices, the function returns the conjugate transpose (conjg(transpose(a))).
• For real or integer matrices, the function returns the transpose (transpose(a)).

Prior art

• SciPy: A.H (H operator)
• NumPy: A.H (H operator)

cc: @jvdp1 @jalvesz @loiseaujc