Implement graphviz printer for SampleNode
Remove dead code
Implement graphviz printer for TableCommitNode
Implement graphviz printer for TableWriterNode
Add session properties to query page in UI
Make partial aggregation memory limit configurable
Fix distributed joins

Use hash distribution, instead of hash distribution followed by
broadcast (which is just broadcast)
Add session property to turn on "big query" mode
Add session properties to query completion events
Fix class loader issues for Raptor ORC writer
Move ClassLoaderSafeConnectorPageSourceProvider to SPI
Add utility for parsing Hive partition keys
Change HiveSplit to carry effective predicate
Fix ORC predicate filtering
Set context class loader for Hadoop FileSystem
Remove bad checkCast from DWRF long stream
Improve unknown value stream error message
Fix ORC map writer for null keys

Map entries with a null key are ignored (not rendered)
Reset in-dictionary stream when opening the stripe or row group
Reset slice dictionary stream for safety