Measure time spent in engine instead of "model", what was too generic

Now there is clear division between time spent in engine and all
additional work made by Modeler.

This gives us much more information, e.g. now we can assess time spent
on scripts execution by comparing "tick" value with sum of "engine"
and "JS rendering".
Add new benchmark: simple model and rendering + really heavy script

It shows how we can asses time spent on script execution. Run this
benchmark and take a look on "engine" + "JS rendering" vs "tick".