remove dead code

Nest joins only if required and fix some issues with complex joins

found by UCDetector

Fix obscure error on non-standard SELECT * FROM A LEFT JOIN B NATURAL JOIN C

Move some JOIN tests from testScript.sql to own file

Remove unused parameters from readJoin() and readTableFilter()

Handle first and last arguments of FunctionIndex.find()

Remove DbSettings.nestedJoins

Convert duplicate anonymous classes in TableFilter to nested for reuse