Presto: Add Presto Druid connector

[findepi]

• [x] first version of Druid connector (https://github.com/prestosql/presto/pull/3522)
• [x] documentation (https://github.com/prestosql/presto/issues/4110)
• [x] full AbstractTestIntegrationSmokeTest for Druid (https://github.com/prestosql/presto/issues/4116)
• [ ] Aggregation pushdown for Druid (https://github.com/prestosql/presto/issues/4109, https://github.com/prestosql/presto/issues/4111)

[Parth-Brahmbhatt]

We are interested in this work , let us know when the connector APIs are updated to expose aggregte pushdown and we can help with this development.

[kokosing]

How about adding druid connector that does not yet support aggregation pushdown? Then we could only focus on aggregation pushdown which itself could be non trivial to do.

[findepi]

@Parth-Brahmbhatt @kokosing see discussion @ https://prestosql.slack.com/archives/CHD6386E4/p1571816266008200

[findepi]

Initial version of Druid connector (#3522) is merged.