Adds image playback

Added image playback code (lib, server, server-side blockly)
Fixed docs removing unimplemented messages
Lowercased port name in digital.js
[wip] Working revision for images

Added spawning in backend
Fixed media handling in image & video so they use MediaHandler to get
the full media path
Added blank_screen method in scenario.image
"Fixed" image display

Added mass murder in fbi to kill fbi subprocesses.
FBI forks and that sucks.
Added fb cleaning code
Fixed MediaManager code

Fixed mediamanager methods, ordering arguments properly
Changed image blockly block
Fixes api call and adds infinite loop

Added infinite loop
Fixed api call to get media list
Fixes function call name

Function changed name, fixed call accordingly
Fixes blockly div integration \o/

Finally...