Refactor BurstDispatcher to allow chaining.
Add NumTransactionsBurstDispatcher
Make BurstRepository.Bursts() return an error too
Make SnapshotRepository.Snapshots() return an error too
Empty bursts are not stored instead of throwing error
Move ReadBurst() and ReadSnapshot() to BurstId and RepositoryId
Add DirBurstRepository
Improve Close() handling in DefaultDatabase.Close()
Improve Close() handling in ApplySnapshot()
Return two errors in Database.Write() to improve error handling
Add DirSnapshotRepository
Change signature of ApplyBursts because of godoc