NEMeetingSubStreamConfiguration 成员列表

成员的完整列表，这些成员属于 NEMeetingSubStreamConfiguration,包括所有继承而来的类成员

	bitrate	NEMeetingSubStreamConfiguration
	contentPrefer	NEMeetingSubStreamConfiguration
	degradationPrefer	NEMeetingSubStreamConfiguration
	frameRate	NEMeetingSubStreamConfiguration
	minBitrate	NEMeetingSubStreamConfiguration
	minFrameRate	NEMeetingSubStreamConfiguration
	videoProfile	NEMeetingSubStreamConfiguration