Provide codec information on transcoded videos

Currently, transcoded videos are represented in a document with the following schema:

{
    "name": "MP4 480p",
    "content": {
        ...,
        "mime-type": "video/mp4",
        ...
    },
    "info": {
        ...,
        "streams": [
            {
                "codec": "h264 (High) (avc1 / 0x31637661)",
                ...
            },
            {
                "codec": "aac (LC) (mp4a / 0x6134706D)",
                ...
            }
        ],
        ...
    }
}

Browsers need codec information to be able to better estimate if they can render a certain video. Currently, we are only using mime-type information. However, sometimes this is not enough (check ELEMENTS-1492).

Even though we have codec information available inside info.streams object, we need to do some parsing to get the right format accepted by the source element.

It would be helpful to include a property inside the document.properties['vid:transcodedVideos'] schema with information about codecs being used, for example:

codecs: "avc1, mp4a";