Create a base implementation for DeleteOperation (DRY)
More refactoring of btree tests into direct btree tests
Cleaner shutdown of servers in integration tests
Fixed package on structured tests
Close down the redis endpoint cleanly
Be sure to actually shutdown the redis endpoint when we shutdown the server
Store keys in a system keyspace

Added the idea of complex operations (multi-row operations)
Added system keyspaces
StructuredSetOperation stores each of the keys
Scan can now be filtered by keyspace (inefficiently!)