Mconf akka transcoding

[pedrobmarin]

Items included in this pull request:

• merged Mario's akka-transcode from SIP project;
• replaced FFmpeg processes in bbb-video with akka-transcode calls;
• and started H264 to H263 transcode logic inside deskshare module for Apple mobile clients.

Tested using one mobile device and it worked as expected. But I think a scenario with more than one mobile user should be considered.

Deskshare's modifications could not be tested in this branch. I just made sure it didn't break anything so this could go up to the MconfDeskshare's branches. I'm very confused about the future of this module. It will probably be gone in a couple of months and that's why I'm already including this changes here.

Last but not least, transcoding high quality videos could be a problem. Got some high CPU usage in those cases. We should discuss what to do about it and probably set a limit within the akka-transcode module.

[pedrobmarin]

Made another pull request without the extra deskshare features