commands: add admin namespace In order to stop abusing the 'debug' namespace for non-debug command, it adds a new 'admin' namespace dedicated to 'admin' operations on a repository (i.e commands suitable for administration tasks). This namespace entry would be used to migrate in the future some existing commands from the 'debug' namespace, or other top level commands that may not be directly exposed to end users. (verify command is a perfect candidate for this case)