Fix json_array_get throws NPE

Fix for #922
Document jason_array_get function
Add 0.55 release notes
Minor fixes to release notes
Do not apply table sampling a data source without splits
Add docs for explain distributed
Fix hash distributed aggregations

Split distribution strategy and output buffer partition strategy
Upgrade to presto hive-apache 0.4
[maven-release-plugin] prepare release 0.55
[maven-release-plugin] prepare for next development iteration
Add ReadOnlyConnectorMetadata
Minor native metadata cleanups
Make native column IDs local to the table
Add missing binding for initial set
Allow explaining any type of statement
Fix task completion for partitioned drivers
Add class name to exception message
Distinguish between missing and empty files
Metadata changes for creating tables
Add checkType utility method