add multistream bin

[ppettit]

captures a v4l2 video stream and pulse audio stream in a single
(mpegts by default) file.

I've found this helps keep everything in sync better. I am using with a datapath card and usb mic but it should work for any v4l2/pulse combination.

simple example profile:

[data]
name = Keele_Default


[track1]
name = av
device = multistream
location = /dev/video0
file = lecture.ts
flavor = presentation
caps = video/x-raw,framerate=25/1,width=1280,height=720
videosink = ximagesink
caps-preview = videoconvert
videoencoder = vaapipostproc ! vaapih264enc

audiolocation = alsa_input.usb-Samson_Technologies_Samson_UB1-00.analog-stereo
amplification = 2.0
audioencoder = voaacenc

[Alfro]

After we test this more, we will add it to the future 2.1 release.
Thank you. :)