adaptivedemux: Provide API for being able to set properties on internal HTTP (and other) sources

Submitted by pot..@..ty.com

Description

I hope you will forgive me that I'm not good at English.

I have been using the version 1.8.0 of gstreamer.

Now, I am building a pipeline to play the Http Live Streaming(HLS) video.

the http protocol can play on this pipeline.
gst-launch-1.0 souphttpsrc location=http://path/to/hls.m3u8 ! decodebin ! videoconvert ! autovideosink

but, https protocol can't play.
gst-launch-1.0 souphttpsrc ssl-strict=false location=https://path/to/hls.m3u8 ! decodebin ! videoconvert ! autovideosink

By the way, in the case of the mp4 can be played on http protocol.
gst-launch-1.0 souphttpsrc ssl-strict=false location=https://path/to/movie.mp4 ! decodebin ! videoconvert ! autovideosink

Please pointed out if there is a mistake to building a pipeline.

Version: 1.8.0