Replace QString::toAscii by QString::toLatin1

Because former is no longer supported by QT5
Replace QWeakPointer by QPointer
Add BaseChannel and AbstractChannelInterface
Implement BaseConnection and AbstractConnectionInterface
Add BaseConnectionRequestsInterface
Add BaseConnectionContactsInterface
Add BaseChannelTextType
Add BaseChannelMessagesInterface
Add BaseConnectionSimplePresenceInterface
Add BaseConnectionContactListInterface
Add BaseConnectionAddressingInterface
Add BaseChannelServerAuthenticationType
Add BaseChannelCaptchaAuthenticationInterface
Add BaseChannelGroupInterface
cmake: telepathy-service does not depend on telepathy