EasySurrogate development for migration

[djgroen]

We discussed how to make surrogates for Flee, and converged on two possibilities:

1. We apply mulitlevel monte carlo, to do runs with reduced # of agents, and reproduce sensitivity analysis at an original resolution,
2. Apply HDMR (Hi-dimensional model representations) to perform SC/Sobol sensitivity analysis with a vastly reduced number of runs.

[wedeling]

Number 2 is now underway with the dimension adaptive sampler, but as part of EasyVVUQ