Eager-create various renderers for faster initial interaction

[xeolabs]

Pre-initialize certain renderers that would otherwise be lazy-initialised on user interaction, such as picking or emphasis, so that there is no delay when user first begins interacting with the viewer.

These include:

1. Mesh picking renderers
2. Surface picking renderers
3. Snapping renderers
4. Silhouette renderers

(1,2) enables fast startup on camera interaction, which uses surface picking to find camera distance to object on line of sight, in order to regulate camera forward/backwards speed.
(3) enabled fast start-up when snapping to vertices for measurement.
(4) enables fast start-up when highlighting and selecting objects.