Add long option for verbosity changes

Only long options are supported in configuration files. "-v" is the only
short option which doesn't have a corresponding long option, therefore
users wouldn't be able to setup verbosity in configuration files without
this patch.

Signed-off-by: Veronika Kabatova <vkabatov@redhat.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>