QoL improvements + semi-transparent option for geometries + vector screenshots (svg)

[dmarkh]

Would be great to have the following:

1. QoL: an option to disable auto-loading of the geometry and event data upon start.
2. QoL: pause rendering while the user is in the "Configure" menu, or an option to repaint canvas ONLY when the user clicks/drags the scene. My laptop's GPU is burning while nothing but the configuration menu is being displayed.
3. Feature: an option to display geometry as semi-transparent instead of solid shapes. Full but semi-transparent tracker geometry + opaque tracks and hits = great for tracking verifications/checks.
4. Feature: SVG format for screenshots. Papers and posters benefit from having scalable vector images. Some examples:
   https://www.star.bnl.gov/~iraklic/EventDisplay/Selected/SVG/