In this commit, we add a new package-level function to emulate the
existing Batch interface for bbolt. We do this via a new super-set
interface which is then checked against in the main implementation of
the Batch method.
In this commit, we add the trio of sequence based methods that bbolt
ships with to the main bucket interface. We do this in order to easily
allow walletdb as is to be slotted into place where bbolt is currently
used, without sacrificing any functionality.
