Based on Pubby 0.3.3.

It supports requesting multi-URI-base (either sub-domain or URL path) data in the same sparql query point.

1. Forward URI Base to pubby (with prefix), e.g., http://data.crystalbridges.org/ is forwarded to http://data.americanartcollaborative.org/cbm/

2. In config.ttl, add mapping rules:

   conf:webBase <http://data.americanartcollaborative.org/>
   conf:dataset [
       ...
       conf:multiURIMapping [
           conf:multiURIPrefix "cbm"; # required
           conf:multiURIBase <http://data.crystalbridges.org/>; # required
           conf:multiURIName "Crystal Bridges Museum of American Art";
           conf:multiURIHomepage <http://crystalbridges.org/>;
       ];
   ];