[telepathy] Remove unique suffix on the Telepathy handler name

There is no point in registering as a unique handler unless there can be
multiple instances of the handler, and it makes the exact name
unpredictable.
[telepathy] Use normal ensure functions instead of ensureAndHandle for creating channels

The ensureAndHandle variants create and register a handler instance
internally, then create the channel request with that handler as the
preferred one. Since we already have our own handler published, that's a
lot of unnecessary and slow dbus traffic and potential for bugs.
[telepathy] Share the Tp::AccountManager instance with Tp::ClientRegistrar

This allows the accounts and connections created by ClientRegistrar to
be the same as those created via that AccountManager directly.
[telepathy] Remove useless and unused handlerAdapters map

QDBusAbstractAdaptor classes are freed automatically when the parent
object is.
Merge pull request #33 from special/telepathy-cleanup

[voicecall] Minor cleanup to TelepathyQt usage in the provider plugin