Load schemas lazily in example-http connector

Eagerly loading the metadata prevents the server from starting if the remote
metadata is not available (e.g. when developing locally without an internet
connection).
Minor CLI cleanup
Fix CLI hang after USE statement
Update required maven version in docs
Add Hive format test for null lists
Fix invalid expression types

This can cause a NPE in the FunctionRegistry because we end up with
arguments that have no type
Include special datetime functions in list
Minor cleanup of PluginManager
Add slice to parent first class list
Fix rendering of domain values in explain output

Values need to be rendered using the cast to varchar function for the
relevant type instead of just calling toString on the values
Add missing period
Update documentation for datetime
Fix typo
Add documentation for datetime types
Add 0.66 release notes
Update to Airlift 0.88
[maven-release-plugin] prepare release 0.66
[maven-release-plugin] prepare for next development iteration
Fix generating invalid query plans
Fix resource leak in HiveSplitSource when queries terminate early

Hive queries that don't consume all splits can leak threads that get
stuck trying to acquire the semaphore that controls how many HDFS
tree walkers run concurrently.

This change makes split sources closeable to allow for proper cleanup.