Ordinary database engine is deprecated but there is no simple mean to change database engine to Atomic for existing databases.

Possible options:
- ALTER DATABASE MODIFY ENGINE query.
- Flag that triggers migration at ClickHouse startup.

The latter should be easier to implement. 

#include <Storages/StorageLog.h>
#include <Storages/StorageFactory.h>
#include <Common/Exception.h>
#include <Common/StringUtils/StringUtils.h>
#include <Common/typeid_cast.h>
#include <Interpreters/evaluateConstantExpression.h>
#include <IO/LimitReadBuffer.h>
#include <IO/ReadBufferFromFileBase.h>
#include <IO/ReadHelpers.h>
#include <IO/WriteBufferFromFileBase.h>
#include <IO/WriteHelpers.h>
#include <IO/copyData.h>
#include <Compression/CompressedReadBuffer.h>
#include <Compression/CompressedWriteBuffer.h>