Attacking the "dbconnection.queryForSelect /
sresults.SelectResults don't use sqlbuilder.Select"
issue a piece at a time, and I needed this for a
sqlbuilder.Select does not know how to handle
sqlbuilder.SQLJoin instances. This diff adds the logic
from dbconnection._fixTablesForJoins and
dbconnection._addJoins to Select, taking a "join"
parameter as SQLObject.select/sresults.SelectResults does.
Trivial test added to the other tests of
sqlbuilder.Select, not a realistic use of a SQLJoin