BaseConnectionRequestsInterface: Fixed createChannel() argument checks.
!Hackish! BaseChannelMessagesInterface::sendMessage: Token added to message header.
Allowed subclass of Tp::ReceivedMessage
BaseChannelMessagesInterface: Fixed timestamp of sent messages.
BaseConnection::Private: "parent" member renamed to clear "connection".
BaseConnection: Request map argument added to some channel related methods.

Argument added to {create,ensure}Channel() methods and it's callbacks.

Request map can contain important details, so should be passed to
underlying creation methods.

Added BaseConnection::Private::getChannelPropertiesFromRequest() method.
BaseConnection: Improved Private::getChannelPropertiesFromRequest().

Implemented handle type detection for conference requests.
BaseConnection: Requests interface added as integral part.

Requests interface is mandatory. It will be merged into main
Connection interface at some point in future.