* services: add pagination and filter support to info RPC.
* cli: add filter flag to service info command.
* docs: add pagination and filter details to services info API.
* paginator: minor updates to comment and func signature.
In the same manner as the delete RPC, the list and read service
registration endpoints can be called either by external operators
or Nomad nodes. The latter occurs when a template is being
rendered which includes Nomad API template funcs. In this case,
the auth token is looked up as the node secret ID for auth.