Refactor DbModel and DbView: they are combined, but the key-value store is split out.
Refactor DbModel and DbView: they are combined, but the key-value store is split out.

stvstnfrd/xblock-sdk,open-craft/XBlock,edx-solutions/XBlock,lovehhf/xblock-sdk,lovehhf/xblock-sdk,stvstnfrd/xblock-sdk,jamiefolsom/xblock-sdk,edx-solutions/xblock-sdk,Pilou81715/hackathon_edX,Lyla-Fischer/xblock-sdk,nagyistoce/edx-XBlock,dcadams/xblock-sdk,edx-solutions/XBlock,jamiefolsom/xblock-sdk,edx/XBlock,nagyistoce/edx-xblock-sdk,4eek/XBlock,open-craft/XBlock,edx/XBlock,cpennington/XBlock,edx/xblock-sdk,cpennington/XBlock,cpennington/XBlock,jamiefolsom/xblock-sdk,edx/xblock-sdk,jamiefolsom/xblock-sdk,Lyla-Fischer/xblock-sdk,lovehhf/xblock-sdk,edx-solutions/xblock-sdk,edx-solutions/xblock-sdk,Pilou81715/hackathon_edX,4eek/XBlock,dcadams/xblock-sdk,lovehhf/XBlock,dcadams/xblock-sdk,mitodl/XBlock,nagyistoce/edx-XBlock,lovehhf/XBlock,EDUlib/XBlock,mitodl/XBlock,Pilou81715/hackathon_edX,stvstnfrd/xblock-sdk,lovehhf/xblock-sdk,EDUlib/XBlock,edx/xblock-sdk,Pilou81715/hackathon_edX,edx-solutions/xblock-sdk,Lyla-Fischer/xblock-sdk,nagyistoce/edx-xblock-sdk,nagyistoce/edx-xblock-sdk,nagyistoce/edx-xblock-sdk