GT-101 Add pass-through options usage hint

[nikita-vanyasin]

Closes #222

[nikita-vanyasin]

Example output (will be printed it if --help or unsupported argument was provided):

Passing through other database options:
      --args.agents.<xxx>=<value>              Passed through to all agent instances as --<xxx>=<value>
      --args.all.<xxx>=<value>                 Passed through to all server instances as --<xxx>=<value>
      --args.coordinators.<xxx>=<value>        Passed through to all coordinator instances as --<xxx>=<value>
      --args.dbservers.<xxx>=<value>           Passed through to all dbserver instances as --<xxx>=<value>
      --args.sync.<xxx>=<value>                Passed through to all sync instances as --<xxx>=<value>
      --args.syncmasters.<xxx>=<value>         Passed through to all sync master instances as --<xxx>=<value>
      --args.syncworkers.<xxx>=<value>         Passed through to all sync master instances as --<xxx>=<value>
      --envs.agents.<xxx>=<value>              Env passed to all agent instances as <xxx>=<value>
      --envs.all.<xxx>=<value>                 Env passed to all server instances as <xxx>=<value>
      --envs.coordinators.<xxx>=<value>        Env passed to all coordinator instances as <xxx>=<value>
      --envs.dbservers.<xxx>=<value>           Env passed to all dbserver instances as <xxx>=<value>
      --envs.sync.<xxx>=<value>                Env passed to all sync instances as <xxx>=<value>
      --envs.syncmasters.<xxx>=<value>         Env passed to all sync master instances as <xxx>=<value>
      --envs.syncworkers.<xxx>=<value>         Env passed to all sync master instances as <xxx>=<value>

[informalict]

LGTM

[informalict]

LGTM