Fix data races in Baysor #162
Description
I discovered that the new Julia version changed how they manage threads, and the implementation of the old parallelism can lead to data races now. I need to fix that first.
While some of my EM code it's said to be not thread-safe. There are also crushes from ProgressMeter on threaded loops, but I don't see why they would happen. I can just disable it for now.