Update transaction log operations to properly interact with RocksDB

[kriszyp]

As a corollary to #158, we should ensure that all the transaction log operations properly interact with RocksDB and LMDB. Here is what I propose:

• read_log - Unchanged. This has nothing to do with transaction logs. Transaction logs and applications are as similar as candy bars and sports bars.
• read_transaction_log - Should call Table.getHistory() like read_audit_log does.
• delete_transaction_log_before - delete_transaction_log_before needs to use RocksDB's purgeLogs #158
• read_audit_log - Unchanged except that we should include a message saying it is deprecated.
• delete_audit_logs_before - Should throw an error in RocksDB indicating that it is unsupported and delete_transaction_log_before should be used instead. (Continues to work on LMDB).
• Make sure that we accept database as a property instead of schema.