Use newtype.
Simplify data structure of Projection type.
Remove redundant paren.
Add shared join product type.
Remove old unused definitions.
Remove redundant definition.
Module renamed.

--HG--
rename : relational-join/src/Database/Relational/Query/Internal/ShowS.hs => relational-join/src/Database/Relational/Query/Internal/String.hs
Definition moved and integrated.
Renamed definition.
Moved definition.
Definition moved.
Add ListProjection type and show rule.
Definition moved.
Fix typing of `in'` operator.