Version 3.4.21

Added back option for external style sheets:
  Added $CSS_FILE config variable.
  Added function Load_style_sheet()
System_Setup(): trim spaces from $excluded_list values.
Table_of_Files(): $excluded_list can now also excludes folders, not just files.
  (Folders had been explicitly un-excluded, but I don't remember why.)
[Edit HTML] button now reads [Edit SOURCE]
Page_Title(): added option for ($page == "copyfolder")
In Output page contents section, adjusted call to load style sheet.
Tweaked a couple css defaults