Feature: Add estimation of Mixing Time

[HaHeho]

Just to keep this idea around.

Currently, the mixing time (transition between early and late reverberation) has to be specified by the user i.e., adjusted in case the default of 80ms yields implausible results. It would be desired if the mixing time could be estimated based on the measurement data, e.g. based on the analysed echo density of the monaural room impulse response [1].

[1] Lindau, A., Kosanke, L., & Weinzierl, S. (2012). Perceptual evaluation of physical predictors of the mixing time in binaural room impulse responses. Journal of the Audio Engineering Society, 60(11), 887–898. https://www.aes.org/e-lib/browse.cfm?elib=16633