HAMMER Utilities: Feature add

HAMMER Utilities: Feature add

Add a new command 'synctid <filesystem>' which provides a formal transaction
id representing the state of the filesystem as of when it is called.  The
filesystem will be properly synced by the command and an interlocked
timestamp will be returned.

Remove the -x option, remove the calls to sync() by the 'now' and 'now64'
directives.  No longer sleep for one second in 'now'.  Document that these
directives do not return a guaranteed transaction id.