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.
Move optimizer to linq4j, improve translation of strict functions