This is the step where the timeline graph gets colored with the individual log
level colors. It's roughly 4.5 times faster now. Probably can be made even
better, the code also needs a cleanup.
RangeFilteredLogModel is gone. The functionality is trivially implemented in
FilteredLogModel now. Changing the range is now O(log n) at worst (was O(n) at
best, for rewriting the arrays). Stacking filtered models is not supported
anymore, which simplifies the code.