Add new way to set requestable channel classes on channel manager
Add new way to set requestable channel classes on channel manager

We can pass the whole classes dictionary instead of splitting it. This way, the dict can be only specified once in the Protocol _requestable_channels property in CMs. Deprecated ways of specifying requestable channel classes are still supported.

max-posedon/telepathy-python,freedesktop-unofficial-mirror/telepathy__telepathy-python,freedesktop-unofficial-mirror/telepathy__telepathy-python,max-posedon/telepathy-python,detrout/telepathy-python,detrout/telepathy-python