Use CREATE OR REPLACE DICTIONARY to avoid data loss (#392)

[the4thamigo-uk]

Summary

Dropping dictionary during model build can break anything that is currently running that depends on it. In particular materialized views that process high volumes of data, can miss processing data if they use a dictionary that is temporarily dropped.

Checklist

Delete items not relevant to your PR:

• Unit and integration tests covering the common scenarios were added
• [ X] A human-readable description of the changes was provided to include in CHANGELOG
• For significant changes, documentation in https://github.com/ClickHouse/clickhouse-docs was updated with further explanations or tutorials