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)