hard-coded removal of special characters in historical_report_purge()

[ablaette]

We have relaxed the regex for data cleaning successively. Now we have these steps in historical_report_purge():

  data[["Message"]] <- gsub("\\&", "+", data[["Message"]])
  data[["Message"]] <- gsub("<", "", data[["Message"]])
  data[["Message"]] <- gsub(">", "", data[["Message"]])
  data[["Message"]] <- gsub("[^-0-9a-zA-ZäöüÄÖÜß\\.,!\\?:;#/ ]+", "", data[["Message"]])

It would be better to have a arguments/options rather than this hard-coded approach.