Add tests with NumPy only when NumPy is found.

Also removed TestNumPy.cmake. One should use the newer
find_python_module() API instead.

Change-Id: Ie40ede812a2d819d6e5e0214d823a82a2964243a
Merge topic 'test_max' into next

96e4410d Add tests with NumPy only when NumPy is found.