Remove setwd() from image output

[abossers-uu]

Please remove the setwd(wd) in the plotting functions (before ggsave) and change it to something like paste0(wd,"/",filename)

In Rstudio when running parts of the FEAST code in chuncks (the default) it complains/aborts onthe setwd argument. You can still use the functions but only with for instance "./" as the path.