1. fixes a lot of stuff in the script files:
   .there are 3 scripts now: bench.py, plot.py and bench-plot.py
   .one can state the number of threads and the base of multiplier

2. adds some generic xkaapi files, not used at the moment since they are
   just copies from the xkaapi repository. will be integrated in the F4RT
   code in the next steps
removes some old benchmark files from repository