Add a bunch of unit tests for nested joins of different types.
NB: Some of these expected plans are *wrong* and will be changed / fixed in a later commit.
Undo 2375.3.2: they won't occur adjacent any more when placed correctly.
Stop when get to one of the special join operators: they all have a definite scope.
Enhace Project adding to handle new cases from having to stop sooner.
Also add a few more comments about what this mechanism does.
Update expected results.
merge mmcm: Correctly place operators added to implement non-group outer- and semi- joins.

https://code.launchpad.net/~mmcm/akiban-server/sql-nested-map-folder/+merge/177664