Fix https://github.com/julianhyde/optiq/issues/205, "Suspicious map.get in VolcanoPlanner.reregister".
Fix https://github.com/julianhyde/optiq/issues/238, "Add adapter that generates TPC-H data".

Added TpchSchemaFactory. TPC-H tests are run if -Doptiq.test.slow=true is specified.
Some TPC-H columns have type DATE.
Remove some obsolete classes.
Remove unused constructor parameter.
Fix https://github.com/julianhyde/optiq/issues/242, "SplunkAdapterTest fails".

The Splunk adapter had been broken by various changes, including the factoring out of Avatica JDBC and removing the schema parent from a table. SplunkAdapterTest now succeeds, and can be run as part of the regular suite if you specify -Doptiq.test.splunk=true.
SplunkAdapterTest now uses the same Foodmart database as JdbcTest.

Begin support for a mock Splunk connection; when it is a complete, you will be able to run the Splunk test suite without Splunk being present.
Implement scalar sub-query in SELECT clause.
Fix https://github.com/julianhyde/optiq/issues/175, "Modify Schema SPI to allow caching".

Added "cache" attribute of Schema JSON element; add method contentsHaveChangedSince to Schema SPI (breaking change, if you've written a schema that does not extend AbstractSchema); big rework of how OptiqSchema builds maps of tables, functions and sub-schemas and how it handles case-insensitive matches.
Tweak parallelism of optiq-plus test suite.
Fix https://github.com/julianhyde/optiq/issues/37, "Document JSON model file format"
  Get sub-schemas defined by a Schema SPI, and cache their OptiqSchema wrappers. (Tobi Vollebregt and Julian Hyde)
Move optimizer to linq4j, improve translation of strict functions
Mark SqlFunctions as @Deterministic (with some exceptions), support static final constants generated by linq4j
Upgrade to linq4j-0.3.
Upgrade maven-release-plugin.
Fix https://github.com/julianhyde/optiq/issues/252, "Scalar sub-query that returns 0 rows should become NULL value".
Provide an option to create root schema without the "metadata" schema.
Hush warnings from SplunkAdapterTest if Splunk is not available.
Avoid excessive box and unbox of primitives when using Object[] storage.