MINOR: stats: define the concept of domain for statistics

The domain option will be used to have statistics attached to other
objects than proxies/listeners/servers. At the moment, only the PROXY
domain is available.

Add an argument 'domain' on the 'show stats' cli command to specify the
domain. Only 'domain proxy' is available now. If not specified, proxy
will be considered the default domain.

For HTML output, only proxy statistics will be displayed.
4 files changed