Snapshot e26e3c0294

* Better backoffs with connection retries to avoid hogging the CPU (smcv)
* Cope with CMs with no presence interface (smcv)
* Warn if dbus-python is older than 0.82.0 (smcv)
* Implement PS calls to leave a shared activity (morgs)
* Fix buddy-left signals (morgs)
* Fixed regressions from adding salut (smcv, morgs)