Enable connection pooling in test suite.

Add FoodmartTest to suite (enabled if -Doptiq.test.slow=true).

Switch various callbacks in the test suite from linq4j Function1 to guava Function.

Add test case for [OPTIQ-403].
Fix connection leak in SqlRun
Don't load FoodMartQuerySet unless we have to. It's big.
[OPTIQ-404] MergeProjectRule should not construct RexPrograms for simple mappings

Move ProjectRel.getPermutation() and .isMapping() up to ProjectRelBase.

Fix a bug in RelOptUtil.projectMapping.