- added very slight fade-in effect (css change)
- added resource-loader colors to element "private" attributes
- externalized all on-screen controls to usco-ultiviewer-osc.html / custome element:
 * makes the markup of the viewer itself more clear an manageable
 * will enabled easier swapping of on-screen 2d items independantly of viewer
 * same goes for styling
 * added some related styling adjustements