Require ns to create subject.
Since we don't allow move subject from one ns to another -
drop add/remove subject to/from namespace
Signed-off-by: Denis Kirillov <d.kirillov@yadro.com>
Autorization can be dedicated to a separate contract, iterating over
multiple keys can be costly. Also add committee as "default" admin:
everything is allowed for it.
Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>
