local: Remove capsfilter workaround after the audio source

This should be unneeded now that the bug in osxaudiosrc is fixed.
Update 'scripts'
bridge: Implement PeerHandler.stop() and RenderController.stop()
Replace dump_dot_file with get_dot_data
bridgeserver: Serve pipeline dot dumps from /graph

The dot dumps are then rendered as SVG in the web page by viz.js