Better selection of measurement locations

[josephmckinsey]

1. We could use a preprocessing step. By the time we get to a simulation, we would already a list of nodes where to put measurements.
2. We could do this in the measurement federate itself. This would create the list of measurement locations when the federate first runs.

In the current setup, the measurement federate is taking the list of measurements from the AWS federate directly. This bit of file system trickery will not scale to Docker.