Added model evaluator, status tests, and pre post operator for solving the problem with nox
(Anderson) in the test NeutronicsFuelTempNOX.cpp. Also added the test PowerIterationCoupled.cpp
which solves the k-eigenvalue problem by power iteration, updating the temperature after a fixed
number of power iterations. Included xml input files for use with these the tests.
Apparently also made some other changes that I can't recall.