search: templates hierarchy

* Changes the template hierarchy so index.html is more specific than
  collection.html.

* Adds basic documentation to find your way out.

Signed-off-by: Yoan Blanc <yoan.blanc@cern.ch>
search: PEP8 and PEP257 fixes

Signed-off-by: Yoan Blanc <yoan.blanc@cern.ch>