add bitrate parameter to RTSP cameras

[NiklasNeugebauer]

Adds the bitrate as a parameter. The control was already supported through the jovision interface.

Aditionally, I have made some adjustments to the interface:

• username/ password in the header turned out not to be necessary
• some type hints were missing
• there was an extra channelid in the param dict
• the values to be set are easy to set as an incorrect type without noticing so I added a backup int cast

[denniswittich]

Looks good. Tests with jovision camera successful.