Fixed empty Sequence steps save/load causing QLC+ (and the user) to freak out

Inverted VC Cue list "next step" slider to reflect external controllers faders
Bump to 4.4.0 beta2 (for now)
Added feedbacks to VC Cue List crossfade sliders

VC Cue List manual crossfade when sliders are not linked now goes to next cue when sliders reach their opposite ends
Fixed potential crash when closing QLC+ and not using Audio input triggers
Fixed show manager sequence creation not updating function manager correctly
Fixed Function Manager sequence deletion removing also its parent Scene
Updated german translations (thanks to Heiko Fanieng)
Save and load IDs also for VC widgets
VC Widgets ID attached to Audio Triggers are now saved and loaded into projects

Filtered audio triggers only when QLC+ is in operate mode
Added code to use QtSerialPort if present. To be done: intensive tests !

Added RX input to Enttec DMX USB PRO dongle
Fixture Editor is now shiny and colorful (as someone said)
Restored VC Cue list "next step" slider to inverted appearance and fixed feedbacks
Added Fixture: Blizzard Lighting Blade RGBW (thanks to James Elliott)

Added Fixture: Stairville MH-X50+ (thanks to Guillaume Rousseau)
Fixed OLA plugin to build against version 0.8.30 (thanks to Rowan Deppeler)
Improved ArtNet information panel + updated translations
Updated translations
Changed function copy name to respect alphabetic order

Updated translations
Updated VC Cue List documentation
French Translation 4.4.0
Merge pull request #153 from NiKoyes/master

French Translation
Give sliders a look closer to real consoles
VC Sliders can now be turned into knobs ! (to be completed and tested)