[BUG #7208] removed unused code
[BUG 7208] disabled web server generated 'index.html'; add support for empty dirs

- (enhance) web server generated 'index.html' files were previously stored
  (like wget does); but this creates artefacts which are not in the original
  SVN source tree (they didn't hurt so far, but are ugly anyway)
- repository-based 'index.html' files are listed in the SVN view and are
  downloaded nevertheless
- since artifical index.html's are not saved anymore, directories need to be
  handled explicitly (this becomes apparent with empty dirs)
[BUG 7208] add alternate ContribLoader, for Allura platform