venelin/PCMBase: Used for MGPM inference in mammal data and simulations

This PCMBase version contains major enhancements of the PCMTree module. Examples for the most important functions in the module are now included in the help-pages for the PCMTree* functions. This PCMBase version was used for the analysis of mammal brain and body mass measurements and simulation study included in the article "Automatic Generation of Evolutionary Hypotheses Using Mixed Gaussian Phylogenetic Models" (currently in review).