* For products that are directories (like manuals), allow a default

suffix other than index.html to be declared.  E.g. if a build does

    echo "doc manual $out manual.html" >> $out/nix-support/hydra-build-products

  the default link for the product is

    http://localhost:3000/build/417/download/1/manual.html

  but other files are also accessible, e.g.
    
    http://localhost:3000/build/417/download/1/style.css

src/sql/hydra.sql

@@ -140,6 +140,7 @@ create table BuildProducts (
     path          text,
     name          text not null, -- generally just the filename part of `path'
     description   text, -- optionally, some description of this file/directory
+    defaultPath   text, -- if `path' is a directory, the default file relative to `path' to be served
     primary key   (build, productnr),
     foreign key   (build) references Builds(id) on delete cascade -- ignored by sqlite
 );