Handler.Capabilities: explain how caps of a running client trump the .client file
Handler.Capabilities: explain how caps of a running client trump the .client file

Exactly how to handle the "Empathy's caps depend whether GStreamer can do
H264" use case will be resolved later, so for now, just set some
reasonable constraints.

freedesktop-unofficial-mirror/telepathy__telepathy-spec,TelepathyIM/telepathy-spec