Fix optimizer performance regression
Fix string comparisons and remove unused field
Simplify handling multiple Hadoop versions
Add Hive plugin for Apache Hadoop 2.x
Implement some functions in JDBC driver
Propagate config from split to RecordReader
Add support for reading Hive data from S3
Add support for hash partitioning on multiple channels
Add full support for DISTINCT in aggregations

DISTINCT is processed in a couple stages.
First a marking stage hash partitions the rows on the DISTINCT expression as well as any GROUP BY clause, and then marks the unique rows.
Second the aggregation operators only process the unique rows, if they have a DISTINCT expression
Fix NullPointerException when reading from S3
Use ImmutableEnumSet
Fix use of closed RecordReader
Introduce Signature object for functions
Refactor LocalExecutionPlanner

Replace Multimap with Map, now that all our channels contain only a
single symbol
Add unit test for DISTINCT aggregation on a JOIN
Add catalog and schema to jdbc string
Add documentation for JDBC driver
Add 0.57 release notes
Update snapshot dependencies
[maven-release-plugin] prepare release 0.57