Modify unit test api for reuse

@jpihl I made some changes to the unit test API, the main reason is that when testing the SIMD stuff we have stacks that do not have the packed arithmetic. So the unit tests didn't work .. Now I made it so that there is a reference field in the unit test that is used to compute the expected result. The reference scheme is just simple_online in the basic case anyhow.. I didn't finish it fully - so it needs a bit of work to be finalized. But take a look.