Graham Markall

Note for reviewers: prior discussions on #829

Note for reviewers: prior discussions on #829

Note for reviewers: prior discussions on #829

gpuci run tests (quick check that all is well after the merge, I haven't yet addressed comments)

gpuci run tests

@stuartarchibald Many thanks for the review - I believe I have addressed / responded to all feedback.

gpuci run tests

gpuci run tests

Note: need to check / implement for float16 types where appropriate.

Fruther note: "Need to implement the math subset of functions in NumPy as a priority so as to tell people to switch" @stuartarchibald