React Native doesn't define __filename nor __dirname so do it artisanally. In
addition, this helps with centralizing the configuration passed to loggers.

Moves getCurrentConferenceUrl method to base/connection to allow reuse.
The new location is not ideal, but looks the best based on the imports
required (trying to avoid circular dependencies).

Co-authored-by: Pawel Domas <pawel.domas@jitsi.org>