Add support for DISTINCT in aggregations for simple cases

Supports COUNT(DISTINCT) and DISTINCT in other aggregations, as long as
there is only one DISTINCT expression, and all the aggregations use this
expression. Also, using it with GROUP BY is not supported yet.
Add a summarized print of TableScanNode TupleDomain to cut down on logging size
Documentation for SHOW CATALOGS
Prune the table scan assignments just before plan finalization
Set no more buffers for hash distributed node
Fix querying tables with missing bucket columns
Fix bogus error message in IDEA 13
Fix handling of Hive bucketed tables
Add missing license header
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