Passing both 'bcast_numpy_array' and '_bcast_actx_array_types' was
ill-defined. For example, in the case of an ArrayContext whose thawed
array type is np.ndarray the specification would contradict between
broadcasting the argument numpy_array to return an object array *OR*
peforming the operation with every leaf array.

Consider the example below,

(
- 'Foo: ArrayContainer' whose arithmetic routines are
   generated by `with_container_arithmetic(bcast_numpy=True,
   _bcast_actx_array_types=True)`
- 'actx: ArrayContextT' for whom `np.ndarray` is a valid thawed array
   type.
)

Foo(DOFArray(actx, [38*actx.ones(3, np.float64)])) + np.array([3, 4, 5])
could be either of:
- array([Foo(DOFArray([array([41, 41, 41])])),
         Foo(DOFArray([array([42, 42, 42])])),
         Foo(DOFArray([array([43, 43, 43])]))]), OR,
- Foo(DOFArray(actx, array([41, 42, 43])))

- Deprecate automatic broadcasting of array context arrays
- Warn about uses of numpy array broadcasting, deprecated earlier
- Clarify documentation, warning wording

…across who

Names suggested by @majosm