Port clientswitcher plugin to Gajim

Port over clientswitcher plugin to Gajim

Gajim has ability to change resource headers, so porting clientswitcher as a plugin to Gajim may work. Gajim is not psi xmpp client though . However it would really cool if someone ported this plugin as a plugin you could install in gajim manually or from a repo.

[stokito]

Switching client name is a bad idea. Instead clients should hide their names. So the plugin should be eliminated (eventually).

[Vitozz]

Why is this here? Is it somehow related to the psi project?