Various doc improvements, add history cleaning to COSQLiteStorePersistentRootBackingStore
Add a test for just the backing store
Sketch out the deletion algorithm
Another misstep
Finally maybe a viable deletion algo.
Move attachments code
Fix attachments test
Fix delete test
Fix remaining tests
Scale down performance test so it can be run all the time
Expand branch deletion test a bit
Add more tests, fix test failures.
Misc. cleanup.
Undo convoluted optimisation related to storing the backing store UUID.
Refactor TestSQLiteStore a bit.
Update todo
Store schema name in items
Tidy docs a bit. Add a method for getting a single embedded item's state.
Fix tests. Add missing tests for store