Add SQL documentation
Rename analyzer.approximate-queries-enabled

Change name of config flag to analyzer.experimental-syntax-enabled,
since it's used to gate more than just approximate queries (rescaled
sampling)
Add JDBC feature DatabaseMetaData.getColumns
Change test query logging to include h2 time
Add index to h2 on custkey

Makes test suite almost twice as fast
Make testSampledRightOuterJoin() more obviously correct

Fix typo in expected query for testSampledRightOuterJoin() to use a
RIGHT join instead of a LEFT join
Fix logging for Hive connectors

Without this exclusion, SLF4J uses logback inside the plugin which
causes anything using the SLF4J API to log to stdout.
Implement VALUES
Add more details to time logging in test queries