Call improvements
This patch does three things:
- Fixes compilation errors that may occur if you don't actually have gstreamer packages available while building calling features
- Implements support for respecting the user's default audio device the first time neochat is ran; future work may be required to support the situation where a user changes their default device after first startup.
- Cleans up by removing some long-unused classes which are possibly unused due to some past git magicks.