changed the initial state generation method for the two-layered system so that it also works for the isolated dimer case (still needs to be generalized to non half filling though ...); fixed a floating point cancellation bug in the UncertainQuantity class (it sometimes caused the variance to be negative and hence the standard deviation to be nan); floating point precision control will now only be done during the measuring phase of the MC cycle (because it wouldn't mess up our results if we had precision misses during equilibration ...); threw out some unused code related to cross-platform compatibility (screw MS and Apple! ;-) ...)
merged latest changes from master