One RTSP server, multiple streams

[timmarkhuff]

A refactor of RTSPServer to allow for one server will multiple streams.

Usage looks like this:

server = RTSPServer(port=port)
server.create_stream(get_frame_callback1, width, height, fps, mount_point='/stream0')
server.create_stream(get_frame_callback2, width, height, fps, mount_point='/stream1')
server.start()
time.sleep(n) # keep the server up 
server.stop()

This also fixes a bug where the server only allowed one client per stream. Most of the complexity of this PR is due to special handling to allow multiple clients.

I also added a test for RTSP server/client functionality. This required a little refactor of our CICD setup.

[timmarkhuff]

Factoring out our system dependencies for CICD into this dockerfile seemed like a good idea, but I'm curious what others think.

[honeytung]

Makes sense to me since we have additional dependencies to install now. Good call!

[timmarkhuff]

The changes to RTSPServer are breaking

[honeytung]

LGTM! It would be great to update the README to include the new features but the implementation makes sense!

[honeytung]

Should probably include these in the README.md

[timmarkhuff]

Updated the readme

[honeytung]

Makes sense to me since we have additional dependencies to install now. Good call!