Use persistent flags on parent command in order to inherit flags in
sub-commands. Turn on notary mode of morph client in `subnet` command of
admin utility for notary environments.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
Add `subnet` command which contains all subnet-related commands. Add
sub-commands:
* `create` for creation;
* `remove` for removal;
* `get` for reading;
* `admin` for admin management;
* `client` for client management.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
