Added data sources list and Search Controller

I've added two important UI components today: the data sources list, and
the search controller.

The data sources list allows the user to select a data source from a
series of available data sources passed to it.  I may rewrite this
tonight to use the Jquery UI selectable element.  That seems like it
would be simpler.

The search controller puts this together with the search parameter
specifier and datagrid to control the entire search lifecycle.  Later,
we'll add the map function to this as well.