their referenced column, even if the column
was given a "key" attribute different from
the reflected name.  This is achieved via a
new flag on ForeignKey/ForeignKeyConstraint
called "link_to_name", if True means the given
name is the referred-to column's name, not its
assigned key.
[ticket:650]
- removed column types from sqlite doc, we
aren't going to list out "implementation" types
since they aren't significant and are less present
in 0.6
- mysql will report on missing reflected foreign
key targets in the same way as other dialects
(we can improve that to be immediate within
reflecttable(), but it should be within
ForeignKeyConstraint()).
- postgres dialect can reflect table with
an include_columns list that doesn't include
one or more primary key columns

with a more succinct "dialect.execution_ctx_cls" member

from [ticket:1068].  This feature is on hold
pending further development.

and not its contained expression, if the dialect reports true for supports_simple_order_by_label.
the flag is not propagated forwards, meant to closely mimic the syntax Postgres expects which is
that only a simple name can be in the ORDER BY, not a more complex expression or function call
with the label name embedded (mysql and sqlite support more complex expressions).

This further sets the standard for propigation of **kwargs within compiler, that we can't just send
**kwargs along blindly to each XXX.process() call; whenever a **kwarg needs to propagate through,
most methods will have to be aware of it and know when they should send it on forward and when not.
This was actually already the case with result_map as well.

The supports_simple_order_by dialect flag defaults to True but is conservatively explicitly set to
False on all dialects except SQLite/MySQL/Postgres to start.

[ticket:1068]

- removed ancient descriptor() functions from dialects; replaced with Dialect.name
- removed similarly ancient sys.modules silliness in Engine.name