Silan cue-in/out analysis now moved to airtime_analyzer

* Added a new CuePointAnalyzer using silan (will remove silan stuff from pypo later)
* Makes silan analysis slightly more reliable for certain short files.
* Fixes CC-5961: Audio duration cutoff for WAVE files
* Added unit tests for the new analyzer and improved code coverage slightly
* Added unit tests for WAVE metadata extraction and an invalid WMA file
ReplayGain analysis in airtime_analyzer using python-rgain

* Implemented Replaygain analysis for Ogg Vorbis, MP3, MP4, and FLAC
  using python-rgain
* Added unit tests for ReplayGainAnalyzer
* Squashed stderr output in ReplayGainAnalyzer and CuePointAnalyzer
* Clean up
Removed all ReplayGain and Silan stuff from pypo, plus a bugfix

* Ripped out all the ReplayGain and Silan analysis from pypo, since
  it's now implemented in airtime_analyzer. This fixes a bunch of
  race conditions.
* Also renamed the replaygain field to replay_gain in airtime_analyzer
  to match Airtime.
CC-5739: Added Liquidsoap playability test to airtime_analyzer
Merge branch 'cc-5709-airtime-analyzer' into cc-5709-airtime-analyzer-cloud-storage

Conflicts:
	python_apps/airtime_analyzer/airtime_analyzer/analyzer_pipeline.py
	python_apps/airtime_analyzer/setup.py