Update Skype to 4.3

Needed because 4.2 is no longer allowed to use the service.
Use CMD to allow execution of commands

This is probably also possible with ENTRYPOINT, but I couldn't get it
working (like others at https://github.com/tomparys/docker-skype-
pulseaudio/pull/4)
Install Video4Linux tools and libs

Also combined separate apt-get install lines into one, to save on the
number of Augeas layers created
Add user 'docker' to 'video' group
Give sudo access to user 'docker'

This is not ideal, but is needed to change ownership on any /dev/video*
device (to root:video) as 'docker' each time the image is started.
Merge remote-tracking branch 'origin/master'

Conflicts:
	Dockerfile