ENG-4279 Require absolute path for voltadmin snapshot commands.
Merge pull request #360 from VoltDB/notest-ENG-4279

ENG-4279 Require absolute path for voltadmin snapshot commands.
ENG-4279 Fix argument validation and -h help output.
Merge pull request #365 from VoltDB/notest-ENG-4279

ENG-4279 Fix argument validation and -h help output.
Merge branch 'master' into ENG-4291-statementxml