Media agent for Roku v4.0.2

Updated

• Added contentBitrate attribute to video events. This uses segmentationBitrate if available, and falls back to streamBitrate when necessary.
• Added adBitrate attribute to ad events. The ad bitrate is now extracted using multiple methods and is standardized to bps (bits per second).
• Added timeSinceLastError attribute to error events, reporting the time elapsed since the previous error event.