Bugfix in matrix multiplication in output computation in iosys.LinearIOSystem - #375

Hi,
I believe the _out method in iosys.LinearIOSystem does not perform the matrix multiplication correctly when not using the numpy matrix class, since it uses * instead of dot().
The following snippet reproduces the incorrect behavior:

import numpy as np
import control as ct
if __name__ == '__main__':	
	ct.use_numpy_matrix(flag=False);
	A = np.array([[0.5, 0.7], [0, -0.8]]);
	B = np.array([[0], [1]]);
	C = np.array([[1, 0]]);
	D = np.array([[0]]);
	iosys = ct.iosys.LinearIOSystem(ct.StateSpace(A, B, C, D));
	x0 = np.array([1.1,-0.9]);
	u0 = np.array([0.5]);
	ct.iosys.linearize(iosys, x0, u0);

The change implemented is consistent with what performed by the _rhs method a few lines above, and works with both matrix and ndarray.

Thanks
Francesco