Fix warnings in HiveBucketing
Fix handling of Hive tables bucketed on string
Add 0.68 release notes
Fix Hive bucketing test
[maven-release-plugin] prepare release 0.68
[maven-release-plugin] prepare for next development iteration
Increase parallelism in unit tests to 4
Add timestamp with time zone minus interval year month operator
Support explaining sampled queries
Move drop table logic to NativeMetadata
Static import query execution factories
Used shared executor for query execution
Rename InMemoryMetadata to TestingMetadata
Remove useless check in NativeMetadata
Use checkType in NativeMetadata
Fix warnings in MetadataManager
Update to Hive 0.13
Add support for Hive file formats

Add support for ORC, ORC vectorized, DWRF and Parquet
Add support for Hive DATE type
Verify types in HiveRecordCursorProvider implementations

If a file format does not support a type, throw an exception durint initialization.

Add all new file formats to HiveRecordCursorProviders.