Feature request for Kokkos to provide Kokkos::atomic_fetch_max and atomic_fetch_min

[mrtupek]

We can use the Kokkos::Impl::atomic_fetch_oper(...) mechanism, but this is in the Impl namespace and having hard-coded max and min atomics seems like it would be useful to the community.

[ndellingwood]

Add necessary unit tests, along with other missing tests (e.g. binary operations); see #341 as well.

[hcedwar]

Note: no corresponding functionality in C++11 atomics

[crtrott]

Yeah, but that doesn't mean we shouldn't support it. I rather have us supporting this, than each team doing its own implementation.

[ndellingwood]

In develop branch