ENH: add string replaceAny() method

- takes a search string and a replacement character.
  The replacement character can also be a nul char ('\0'), which
  simply removes the characters.

  Possible uses:

  * Replace reserved characters
      str.replaceAny("<>:", '_');

  * Remove shell meta-characters or reserved filesystem characters
      str.replaceAny("*?<>{}[]:", '\0');