added a counter and event to simulation_process to only allow a single thread to parse results and write them at a time, while no adsm processes are running. updated simulation_process so that each forked process gets its own database connection. Refs #150
updated test to for population link to lookup a new unit id instead of calculating it
added test for multiple simulation threads. fixed issue where migrations would not run on tests due to a stale database connection. added names to test databases so that they can be referenced by views in tests. Refs #150