Update pyfaust.Faust ops (indexing, elt-wise mul., addition).

- Faust indexing: support of np.ndarray as list of indices.
- Support of Faust element-wise multiplication with broadcasting if the other operand is a np.ndarray vector (ndim == 1 or 2).
- Complete __add__: case when operand is a np.ndarray of size 1x1, and broadcasting case F+G where F.shape[1] is 1 and G is a np.ndarray vector.