Add files needed for licensing and versioning

[teodordelibasic-db]

What changes are proposed in this pull request?

Adding the following files:

1. LICENSE - File containing the Databricks license.
2. NOTICE - File containing licenses used by dependencies.
3. MANIFEST.in - What files are contained in the source distribution.
4. CHANGELOG.md - Version changelog in reverse chronological ordering.
5. NEXT_CHANGELOG.md - File that should be updated on each commit with contained changes.

How is this tested?

Manually uploaded to Test PyPI and created a test client project.

[elenagaljak-db]

lgtm