- Check if we have enough permissions to write in directory at the following

- Check if we have enough permissions to write in directory at the following
  points:
  - Before executing a command which creates a new file
  - Before uploading a file
  - Before removing or moving/renaming a file or directory
- oct() does not care about leading zeros, the resulting value is always the
  same.
- The name of the variable which will be replaced by a directory to go back to
  in error.htm was renamed from "{DIR}" to "{BACK}". "{DIR}" caused some
  problems.
- Changed the names of some error messages:
  nocopy -> no_copy
  noedit -> no_edit
  noview -> no_view