Imports of gnatsd command

PathSynopsis
flagPackage flag implements command-line flag parsing.
fmtPackage fmt implements formatted I/O with functions analogous to C's printf and scanf.
github.com/nats-io/gnatsd/serverPackage sublist is a routing mechanism to handle subject distribution and provides a facility to match subjects from published messages to interested subscribers.
osPackage os provides a platform-independent interface to operating system functionality.