Fix warnings in HiveMetastoreClientFactory
Move metastore stats to metastore package
Fix NULLIF semantics

NULLIF now correctly returns a result with the type of the first argument. For instance:

    NULLIF(1.0, 2) => 1.0
    NULLIF(1, 2.0) => 1

Previously, the type of the result was the common supertype of both arguments
Add comment field in DESCRIBE TABLE
Update to new ColumnMetadata api
Change column comment to be empty string instead of null
Configurable Hive SerDe, InputFormat, OutputFormat in CreateTableAsSelect

Closes #1453
added number of runs and fixed time zone header
Factor a TestingPrestoClient out, add a single node server query runner.

This removes the query specific code from the DistributedQueryRunner
and adds a new QueryRunner that uses a real, albeit single-node,
embeded discovery TestingPrestoServer. Unlike the LocalQueryRunner
which fakes a presto engine, this is a full-fledged server.
JsonPath with bracket-notation
Add explicit tokenization step to JSON path