Periodically flush intermediate compilations on disk to avoid recompiling large windows

[msakrejda]

The aggregation section briefly lays out the aggregation mechanism, but it's not clear what happens if the process crashes--are the partial results for the aggregation for the current period lost entirely? Or is cyanite able to recompute the whole window from the raw samples?

[ifesdjeen]

For now they are lost completely. It's a good reminder tho, we need to take care of it too.