Added WilsonLoop tests.
Added simulation refactoring to todo list.
Modified save/load procedures in DataSet to allow types with no save/load attribute.
Moved to generalized measurement functions in Simulation
Fixed a couple of bugs in ensemble loading.
Removed XML stuff as we're moving away from this.
Removed printing of Simulation for now as __str__ needs fixing.
Added tests for Simualation.
Added data files needed for tests.