Remove unused imports
Oops.  testLeftJoinNullable wasn't actually running!
Pull out "extract" functions from PackMap usage
Extract the PM monadic operations
Use PackMap.run to abstract running the monads
Downgrade a FIXME
Remove unused SelectFold
Get rid of parametrised types as we didn't use them
Pull out printing into Internal.Print
Add Internal.Optimize
Reorder code in SqlOpaleye
Three way product test
Optimize.mergeProduct