Space-filling curve traversal for GPU and CPU added

Specify the -H commandline parameter to activate the hilbert-curve
   -> This feature is only available for gridsizes which are a power of two.
      This feature can be modified to work for all gridsizes with small changes.

Further changes include:
  - Command-line bugfix (same arguments have been ambiguous
  - Performance counters were buggy
Merge pull request #1 from springer13/master

Space-filling curve traversal for GPU and CPU added