Automatically reduce video quality when there are multiple video instances.

[bdlukaa]

Currently, the user can choose the rendering quality of the video. It is default to automatic.

The problem
When an user wants to view several cameras at the very same time, the computer will likely hang due to lack of computing power. Rendering a video is a consuming task, rendering multiple videos is even more consuming.

The automatic behavior
Currently, when the rendering resolution is set to automatic, the video resolution is defined by the camera resolution.
Ideally, when there are several cameras at the same time, the video rendering resolution should be automatically lowered to ensure the smoothness of the app.

Additional context
https://forums.bluecherrydvr.com/t/bc-client-3-0-0-beta21-hangs-on-startup/982