New fixtures: Eurolite TSL-200, Velleman Beam Driver 250, Laserworld CS-1000RGB (thanks to Rob Nieuwenhuizen)
Show Manager: added a timing tool to set a Show item start position and total duration

The timing tool does:
- nothing on Audio and Video
- scale Sequences steps
- set duration of EFX and RGB Matrix

ShowRunner: Fixed playback of EFX and RGB Matrix in ShowRunner
Speed Dials: Fixed unwanted time values sent under certain circumstances (see SpeedDial::setSpinValues code comment)
Updated Show Manager documentation