Improve performance by tweaking user-facing values

[Razoric480]

This is just to show that you can get better performance with a few changes to the baseline:

1. Only update the proximity agents every couple seconds instead of every frame
2. Change from a blend to a priority for collision avoidance
3. Increase arrival thresholds and priority zero threshold

There's a period near the start where everyone is bunched up and it's slow, but once some distance has been put between the units, the performance picks up to playable levels. Some more massaging and tweaking, and maybe a more 'collision aware' spawning method could keep that framerate going throughout.

I do still mean to go into the steering framework code itself and make improvements for performance reasons - I already have some ideas for it. But I figured this is pretty demonstrative of the sort of improvements you can make with a few changes.