Fix html5 videonode setDefaultVolume in firefox

Firefox does not notice when the "muted" attribute is added to the video
tag, to properly mute an audio stream you must explicitly set the volume
through the javascript API.
4.0.3 version
Merge branch 'hotfix/4.0.3'
Document a git strategy for working with upstream
DCE customizations roll-up commit.
CS50-inspired paella theme. Includes:

* Styling, color, and icon improvements.
* Use cs50 theme by default, disabling others
* Workflow and tooling improvements
* Add playback rate plugin
* Toggle between four simplified layouts / profiles
* Optimize video profiles for our aspect ratios
* Update git strategy RE the upstream git process refactor
* Style the frameControl plugin, subtle background gradient
* Disable controls autohiding by setting the timeout to a huge value
* Create the "total duration" plugin, show in the control bar