dot(array,array) fails

[BruceSherwood]

On VPython 5, when the dot function arguments involved numpy arrays, the numpy dot function was invoked. Somehow this is broken on VPython 6, which invokes the VPython vector dot function and fails.

[BruceSherwood]

Here is an example that gives an error (no error if a and b are simple 1x3 arrays):

a=array([[1.,2],[3,4]])
b=array([[11.,12],[13,14]])
c=dot(a,b)

[BruceSherwood]

Fixed.