Using lib.* operators in Matrix.reduce_*

[marci543]

Matrix.reduce_vector() cannot be used with lib.GxB_*_MONOID.
The problem might be around this line:
https://github.com/michelp/pygraphblas/blob/7465ef6fcc77c9901869b70ddf1d77a86570c336/pygraphblas/matrix.py#L598

It would be also good to have a version that supports the BinaryOp variant of reduce_vector.

[michelp]

Hmm, i'll check it out, but meanwhile you can so something like vector_reduce(FP32.PLUS_MONOID) agreed a bout the BinaryOp variant.