Release version 4.8.1.

Updated Show Manager documentation
Fixed 4.8.1 changelog date
Dutch translations
Matrix editor: Fade out time is not included in Duration
(found by Giorgio, analysis David Garyga, fix Jano Svitok)
Merge pull request #367 from joepadmiraal/Dutch_translation

Dutch translations update
New fixtures: NJD Spectre, Chauvet Eclipse RGB (thanks to Charles Oldham)

Version bump to 4.8.2 GIT
New fixtures: American DJ Dotz TPar, Abstract Twister 4 (thanks to Charles Oldham)
New fixture: American DJ Galaxian Sky (thanks to Chicken)
New fixtures: Cameo Strobe 3x3.5W, Cameo Strobe 6x10W (thanks to Janosch Frank)
New fixture: Stairville HL-x9 Quad Color Flood 9x8W (thanks to Janosch Frank)
New fixture: American DJ Inno Pocket Scan (thanks to George Qualley)
New fixture: Stairville LED PAR56 10MM-UV (thanks to Hadley Denton)
New fixture: Pulse ECO LED PAR56 (thanks to Charles Oldham)
Virtual Console: give Cue List cross faders the QLC+ style
[WIP] Virtual Console: introducing the VCMatrix widget