New protocol interfaces in Azoth

[Georg Rudoy]

Hi!

I've added a couple of new interfaces to Azoth which may be of
interest to protocol plugin developers. They are:
* IHavePings for contact list entries that, well, support pings. This
API is used by /ping command, for example.
* IHaveQueriableVersion for entries that support querying client
version on demand. This one is used by the /version command, for
example.
* ISupportLastActivity for protocols supporting querying last
activity/connection time of entries and/or uptime of servers. Used by
the /last command, for example.

Of course, plugins can update the corresponding information whenever
they want to without implementing these interfaces, but they can be
useful for on-demand updates.

Oleg, probably some of these will be of use for Acetamide?

--
Georg Rudoy