Better support for accessing stream types.

[alex-w-k]

Add better support for accessing stream types, like video, audio, and subtitles.

For example on this movie the streams section of the XML looks like this:

<Stream id="352782" streamType="1" default="1" codec="h264" index="0" bitrate="12993" language="English" languageCode="eng" bitDepth="8" chromaLocation="left" chromaSubsampling="4:2:0" frameRate="23.976" hasScalingMatrix="0" height="816" level="41" profile="high" refFrames="5" requiredBandwidths="35655,31724,25768,23725,21919,20284,16697,16697" scanType="progressive" title="13993 kbps" width="1920" displayTitle="1080p (H.264)"/>
<Stream id="352783" streamType="2" selected="1" default="1" codec="dca" index="1" channels="6" bitrate="1509" language="English" languageCode="eng" audioChannelLayout="5.1(side)" bitDepth="24" profile="dts" requiredBandwidths="1509,1509,1509,1509,1509,1509,1509,1509" samplingRate="48000" title="Main Audio" displayTitle="English (DTS 5.1)"/>
<Stream id="352784" streamType="2" codec="aac" index="2" channels="2" bitrate="70" language="English" languageCode="eng" audioChannelLayout="stereo" profile="he-aac" requiredBandwidths="71,71,71,71,71,71,71,71" samplingRate="48000" title="Commentary" displayTitle="English (HE-AAC Stereo)"/>
<Stream id="352785" streamType="3" selected="1" default="1" codec="srt" index="3" bitrate="0" language="English" languageCode="eng" requiredBandwidths="1,1,1,1,1,1,1,1" title="srt" displayTitle="English (SRT)"/>
<Stream id="352786" streamType="3" codec="srt" index="4" bitrate="0" language="中文" languageCode="chi" requiredBandwidths="1,1,1,1,1,1,1,1" title="srt" displayTitle="中文 (SRT)"/>

And I'd love a way to do something like: movie.streams.audios or something and have it return these two entries in an array of two objects of audio class or something to that effect:

<Stream id="352783" streamType="2" selected="1" default="1" codec="dca" index="1" channels="6" bitrate="1509" language="English" languageCode="eng" audioChannelLayout="5.1(side)" bitDepth="24" profile="dts" requiredBandwidths="1509,1509,1509,1509,1509,1509,1509,1509" samplingRate="48000" title="Main Audio" displayTitle="English (DTS 5.1)"/>
<Stream id="352784" streamType="2" codec="aac" index="2" channels="2" bitrate="70" language="English" languageCode="eng" audioChannelLayout="stereo" profile="he-aac" requiredBandwidths="71,71,71,71,71,71,71,71" samplingRate="48000" title="Commentary" displayTitle="English (HE-AAC Stereo)"/>

Note that audio is streamType="2" so that should be pretty straight forward, however I was thinking about how to implement this and it would make sense to break each stream type out into its own class, but herein lies the problem. streamType="1" is video and there is already a Video class, so I'm not sure how to go about doing this. What are the thoughts on the best way to tackle this?

Would it be best to leave video out of it and just do audio and subtitles? Or would it be best to name them like StreamVideo, StreamAudio, and StreamSubtitle, though that seems a bit awkward and not super discoverable.