Events, Messages and Query based APIs

Detailed Description

Defines Events, Messages and Query-based APIs.

Modules
	Events: Custom Events API
	Specifies GStreamer custom event functions, used to map events to individual sources which are batched together by Gst-nvstreammux.
	Messages: Custom Message Functions API
	Helper functions for custom GStreamer messages posted by DeepStream GStreamer plugins.
	Query Functions
	Gets information such as the batch size and the number of streams.