Connector capabilities

[surister]

Connector capabilities are defined in: manifest.xml as CrateDB evolve new capabilities might need changing.

Documentation of what every capability means: https://tableau.github.io/connector-plugin-sdk/docs/capabilities

[surister]

#8 Changes CAP_QUERY_TOP_SAMPLE_FAST and CAP_QUERY_TOP_SAMPLE_PERCENT since we believe we don't support it, the manifiest only references TOP as LIMIT so it might make sense. We should get back at this after checking the tests, but it can be done later, having no is safe.