doc: add ability to disambiguate clicmds

doc: add ability to disambiguate clicmds

Multiple daemons have the same CLI commands defined, but the current
directive used to document CLI commands only takes the command
definition string. Since CLI command objects can be cross-referenced
using the :clicmd: directive, and are placed in the index, each object
needs to be unique.

To accomplish this, add a custom directive. This directive extends the
directive class used by sphinx's add_object_type to add a :daemon:
option. By specifying this option where needed, the object name becomes
"(<daemon>) <definition>", disambiguating it.

Signed-off-by: Quentin Young <qlyoung@qlyoung.net>