For Resample.* and QualityPrefs.cpp, this commit has my restructuring for distinguishing constant-rate vs variable-rate resamplers more generally. I think it's complete and ready for const-rate, but I have more review and testing to do for the var-rate cases.
Variable-rate resampling is not implemented here, so Time Tracks are still broken, but this is a milestone in getting to a more general and correct structure.
Also I think this fixes AboutDialog issues Steve noticed.