Master

neaer typo in FCSInterface.c corrected (print statement)

FCS_2_SQRTPI in documentation file interface.tex set to value of FCSDefinitions.h and typo corrected

removal of constants like M_E from lib/p3m/utils.h and lib/p3m/error_estimate.c to prevent redundancy and improve maintenance. Please use the constants from FCSDefinitions.h like FCS_E. current usages in all lib/p3m files were replaced by FCS_constants