2.52.02: BoM-based calculation endpoint; roofing unit conversion improvements

This update exposes C.Scale's bill of materials-based LCA calculation service and includes a number of small improvements to unit handling in the roofing endpoints. 
BoM-based whole life carbon engine
The new api/calculate/bom
 endpoint performs whole life carbon calculations on a set of material quantities ("takeoffs") together with background material data. This endpoint isolates the calculations which transform building quantities into results by life cycle stage and across time. Currently, one item is one takeoff. In the coming weeks, we're adding more support for assemblies. 
Roofing conversion improvements
This update includes a number of improvements to unit conversions in the roofing carbon intensities endpoints. 