G-Cloud division of procurement

Several changes: 

* Remove unused URL parameters, not needed in Backdrop; update stubs and tests; ensure module and collection do not expect these parameters. 
* Use real cumulative count data from Backdrop, now it is available. 

This graph is not yet completely ready to go live, because we need to remove the "currency" option from the graph when the count tab is live. However, I think it makes sense to start merging it now.