PostgreSQL: An error was missing after trying to use tx.Collection() after the transaction was completed.

Conflicts:
	util/sqlgen/benchmark_test.go

Finishing implementation of a simple cache. Generation time was reduced by a factor of 20% to 90% (according to attached benchmarks).

This reverts commit de7dfc95.

Temporary removing QL from travis tests. QL uses a _solaris.go file that throws compile time errors on < go1.3.