Add XML Schema for fixture definitions

The point is to help with checking fixture files
Automatic changes to fixture files:

- added namespace
- fixed some author names
- removed ,,, from author names
- changed decimal , to decimal . in weights
Make Lens degrees type qreal - Robe Robin 600E Beam has max degree 6.5
Add XML namespace when saving files
Update script to use schemas
Fix Martin Roboscan - remove duplicate tag
Improved script - added channels/heads
Fix fine channels in fixture definitions
Normalize Pan/Tilt channel names