Modified Doxyfile to show private member functions if documented
Added doxygen documentation for AbstractPlotter class
fixed creating own 'createFinalScript()' method in PlotterGnuplot instead of overwriting it
Minor change

* added dot.
Added doxygen documentation for PlotterGnuplot class
Added doxygen documentation for PlotterPython class
Added doxygen documentation for PlotterR class
Minor changes

* fixed typo in doxygen comment in PlotterPython.h
* added @see link to AbstractPlotter in PlotterGnuplot.h
* placed @file link in the first comment line with /** as convention says
Merge branch 'feature_doxygen' of github.com:schwald/bencho into feature_doxygen