Using distFun in clusterMany shouldn't use global.env()

[epurdom]

To use distFun with clusterMany, user gives character names of functions and they are looked up in global.env by the internal function .makeDiss. This is problematic and not good use of environments. For example, calling

rmarkdown::render("clusterExperimentTutorial.Rmd",envir=new.env())

crashes because it's run in a new environment so the defined distance functions in the tutorial are not in global.env().