Updated the main graph500 unit test to use the new approach of defining hybrid and vanilla tests.
Deleted the redundent graph500_stepwise unit test file.
Fixed a bug in the stepwise hybrid graph500 algorithm aggregation function.
Added the Graph500 stepwise algorithm to the benchmark.
Added the graph500 stepwise algorithm to the unittests.
Enabled allocting the remote neighbours of the inbox buffers. This is necessary for Graph500 stepwise algorithm.
Changed the thirdparty graph500 benchmark to use the stepwise algorithm.
Added the missing option for edge sort direction to the Graph500 challenge.