Dbt-clickhouse

Bug fix
- Lightweight deletes could fail in environments where the HTTP session was not preserved (such as clusters behind a non-sticky
load balancer). This has been fixed by sending the required settings with every request instead of relying on a SET statement.
A similar approach has been used to persist the 'insert_distributed_sync' setting for Distributed table materializations.

Improvement
- Adds additional experimental support for Distributed table engine models and incremental materialization. See the README for
details. Thanks to [gladkikhtutu](https://github.com/gladkikhtutu) for the contribution!

Bug Fixes
- Fixed two logging/exception handling issues that would cause exception on startup or when handling some exceptions
from the ClickHouse server. Partially addresses https://github.com/ClickHouse/dbt-clickhouse/issues/169.
- Fixed issue with the `on_cluster` macro that would break the exchange tables step of incremental materializations
with an active cluster. Thanks to [Andrew Davis](https://github.com/Savid) for the PR. Closes
https://github.com/ClickHouse/dbt-clickhouse/issues/167

Bug Fix
- Use correct return value for `execute`. This would cause an exception when running hooks. Thanks to
[Sergey Reshetnikov](https://github.com/PrVrSs) for the PR. Closed https://github.com/ClickHouse/dbt-clickhouse/issues/161

Improvement
- Added macros for creating distributed tables. See the `distributed_table.sql` include file. Thanks to
[gladkikhtutu](https://github.com/gladkikhtutu) for the contribution.

Bug fixes
- Create initial dbt database (if not found) on the defined cluster on first run, instead of just the execution node.
Thanks to [Jens Hoevenaars](https://github.com/codenation-nl) for the PR
- Fix the SYSTEM SYNC REPLICA statement when exchanging tables ON CLUSTER for incremental materializations. Thanks to
[Schum](https://github.com/Schum-io) for PR. Closed https://github.com/ClickHouse/dbt-clickhouse/issues/157.

Improvements
- Reduce the number of SQL calls for Modify Comment operations. Thanks to [Konstantin Ilchenko](https://github.com/simpl1g).
- Add "on cluster" to several additional macros to better support distributed tables. Thanks to [Saurabh Bikram](https://github.com/saurabhbikram)
- Add the unique invocation id to temporary "new data" used in `delete+insert` incremental materializations to allow parallel transformations on the same
table. In general parallel transformations are risky, so this approach should only be used when transformations are explicitly limited
to non-overlapping data ranges. Closes https://github.com/ClickHouse/dbt-clickhouse/issues/150