#148 nmap-services-tcp.csv isn't found when calling ID2T from outside it's directory

Caused by 52664946596c410a912e0b77968d827dc9e55b7a The C++ code uses a path relative to the current working directory to find nmap-services-tcp.csv (only used when creating a statistics database), which doesn't work when you're not calling ID2T from inside its directory. The proper solution would probably be to pass the path to ID2T to the C++ code, which would also eliminate the need for statistics_db::getNmapPath().