Pass params to souces when querying

By passing the HTTP parameters to the data source when
querying it, the source can use those extra optional
parameters.  This allows more dynamic querying, like:

http://localhost/ac/tag?q=foo&type=bar

Update the model source to require explicitly defined
parameters, and then check if any of those parameters
are present in the query.

NOTE: This commit requires that you reset your
sources.ex.js.  Just do
cp config/settings/sources.ex.js config/settings/sources.js