- [feature] The of_type() construct on attributes

- [feature] The of_type() construct on attributes
now accepts aliased() class constructs as well
as with_polymorphic constructs, and works with
query.join(), any(), has(), and also
eager loaders subqueryload(), joinedload(),
contains_eager()
[ticket:2438] [ticket:1106]
- a rewrite of the query path system to use an
object based approach for more succinct usage.  the system
has been designed carefully to not add an excessive method overhead.
- [feature] select() features a correlate_except()
method, auto correlates all selectables except those
passed.   Is needed here for the updated any()/has()
functionality.
- remove some old cruft from LoaderStrategy, init(),debug_callable()
- use a namedtuple for _extended_entity_info.  This method should
become standard within the orm internals
- some tweaks to the memory profile tests, number of runs can
be customized to work around pysqlite's very annoying behavior
- try to simplify PropertyOption._get_paths(), rename to _process_paths(),
returns a single list now.  overall works more completely as was needed
for of_type() functionality