[Web Apps] Added a few improvements to the Django application.

1. The Web form method is now GET, rather than POST. As a consequence,
   the form parameters are passed into the URL, which enables to save
   the URL in bookmarks and/or to share searches.
2. The URL parameters are more standard: the query string is now 'q':
   http://search-airports.com/apps/search?q=nce+sfo
3. A "Did you mean xxx?" suggestion, with a link on the corrected
   query string, has been added.
Merge branch 'trunk' into releases