Updated original performance test program.

* Updated the original performance_main program.
    * Does no longer depend on pficommon library.
    * Uses C++11 instead.
    * Works with Eigen 3.2.0.
    * Comes with compile instructions, does not need build system.
    * Behaviour probably slightly changed, compared to the original
      version.
* Updated compile instructions for performance_plot and
  really_simple_example (did not work on my Ubuntu laptop before).