Integrate depacketizer in ExternalOuput adding h264

[lodoyun]

Description
This PR integrates the new Depacketizer into ExternalOutput replacing all the old vp8 depacketizer login. As part of the process of integrating it, this PR updates the Depacketizer to better suit the rest of Erizo naming conventions and removing the throw code.
This PR also adds support for H264 in recording new that we have a compatible depacketizer, that required a minor change in LayerDetectorHandler to start marking the spatial layer of h264 packets (for now it's always 0).

[] It needs and includes Unit Tests

Changes in Client or Server public APIs

[] It includes documentation for these changes in /doc.

[jcague]

LGTM!

[nvazquezg]

@lodoyun This PR allows the creation of recordings using H264 codec? Or the output is still VP8 only?

[lodoyun]

@nvazquezg Yes, H.264 recording is supported for H.264 rooms, meaning Licode won't transcode when recording, it will record in the codec that the room is using.
Also, keep in mind the result is still a .mkv file so you will have to postprocess it to use any other format.

[nvazquezg]

@lodoyun Understood, thanks. To configure a room as H.264 I've set:
{ "mediaConfiguration": "H264_AND_OPUS" }.
Is there anything else I have to do? Because if I try to record in a room configured this way, I get the following error:

ERROR [0x7fdd31ffb700] media.ExternalOutput - Could not find video codec

I traced it to here:

licode/erizo/src/erizo/media/ExternalOutput.cpp

Line 368 in bc4e67c

ELOG_ERROR("Could not find video codec");

Please, tell me if I am doing something wrong or if I need to file an issue.

[yannistseng]

@nvazquezg try this

./scripts/installUbuntuDeps.sh --enable-gpl

[nvazquezg]

@yannistseng that did the trick. Thank you very much! 👍