documented self_predict in gaussian_process.cpp
removed all of the unnecessary n_use variables from the optimize() routines in gaussian_process.cpp
made optimize_grid and optimize_simplex private routines in gaussian_process.h
cleaned up some of the gp::optimize routines
documented gaussian process optimization routines
removed unused variable inversionerr from gaussian_process.cpp
removed more unused variables from gaussian_process.h
reordered min and max in gg.initialize to make it sensible
finished documenting the gp class