Implement an OpenMP parallelized backend wrapping an arbitrary computational backend with state S, algebra A and operations O as openmp_state<S>, openmp_algebra<A> and
openmp_operations<O>.

Implement resize and reduction operations.

Test correctness and performance with all viable backends and find user-friendly solution for parallelized system functions (i.e. allow easy use of system functions written for the computational backend with the parallelized backend, but non-linear operations like moving data between the threads' sub-states should be possible here, too, if required by user)