Expose low level api of insert

[Rachelint]

Summary

A short description of the changes with a link to an open issue.

Checklist

Delete items not relevant to your PR:

• Unit and integration tests covering the common scenarios were added
• A human-readable description of the changes was provided so that we can include it in CHANGELOG later
• For significant changes, documentation in README and https://github.com/ClickHouse/clickhouse-docs was updated with further explanations or tutorials

closes #233 #212

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[slvrtrn]

What is the status of this PR? As CLA is not signed, this is not mergeable.

[Rachelint]

What is the status of this PR? As CLA is not signed, this is not mergeable.

Still working, I will sign it, and make the pr ready this week.