- specifying joins in the from_obj argument of query.select() will

- specifying joins in the from_obj argument of query.select() will
replace the main table of the query, if the table is somewhere within
the given from_obj.  this makes it possible to produce custom joins and
outerjoins in queries without the main table getting added twice.
[ticket:315]
- added join_to and outerjoin_to transformative methods to SelectResults,
to build up join/outerjoin conditions based on property names. also
added select_from to explicitly set from_obj parameter.
- factored "results" arrays from the mapper test suite and into the
"tables" mapper
- added "viewonly" param to docs