Sort FT clusters in decoder
The clusters need to be sorted when making measurements in the FTMeasurementProvider. It was using a const_cast and calling sort on them, which breaks constness of clusters. It should therefore be done in the decoder, or in a separate algorithm. This was the simplest solution.
In general, the FastClusterContainer seems a rather suboptimal way of storing the clusters, especially since a std::lower_bound is needed to find then when making measurements. Some mapping type seems much more appropriate. The MC linking would have to be adapted or both containers kept, but it looks like time could be saved in both the pattern recognition and the fit.