Change-Id: Ida0d01ae9bcc0573b86e24fddea620a38c962822

An :func:`.aliased()` construct can now be passed to the
:meth:`.Query.select_entity_from` method.   Entities will be pulled
from the selectable represented by the :func:`.aliased` construct.
This allows special options for :func:`.aliased` such as
:paramref:`.aliased.adapt_on_names` to be used in conjunction with
:meth:`.Query.select_entity_from`.

Additionally rewrote the docstring for :meth:`.Query.select_entity_from`,
including starting with explicit use of :func:`.aliased` as the
usual idiomatic pattern.  An example using text().columns() is added
as well as the use case from :ticket:`3933` using name matching.

Change-Id: If7e182965236993064a2a086e3b6d55a4f097ca8
Fixes: #3933

tested using pycodestyle version 2.2.0

Fixes: #3885
Change-Id: I5df43adc3aefe318f9eeab72a078247a548ec566
Pull-request: https://github.com/zzzeek/sqlalchemy/pull/343

This is an old parameter no longer relevant to how SQLAlchemy
works, once the Query object was introduced.  By deprecating it
we establish that we aren't supporting non-working use cases
and that we encourage applications to move off of the use of this
parameter.

Fixes: #3394
Change-Id: I25b9a38142a1537bbcb27d3e8b66a8b265140072

To be more descriptive of the use of _mapper_zero(), rename
it to _entity_zero(), but also supply a new _mapper_zero() function
that more strictly returns a mapper.  The existing
_entity_zero() function is renamed to _query_entity_zero.
_only_mapper_zero() is removed as it isn't used.  Divide up the
existing calling functions to refer to the appropriate new method.

Change-Id: I8780c3235e87b4936c6daf64d9d299b22b6e1260
Fixes: #3608

constructs are now importable from the "from sqlalchemy" namespace,
just like every other Core construct.
- The implicit conversion of strings to :func:`.text` constructs
when passed to most builder methods of :func:`.select` as
well as :class:`.Query` now emits a warning with just the
plain string sent.   The textual conversion still proceeds normally,
however.  The only method that accepts a string without a warning
are the "label reference" methods like order_by(), group_by();
these functions will now at compile time attempt to resolve a single
string argument to a column or label expression present in the
selectable; if none is located, the expression still renders, but
you get the warning again. The rationale here is that the implicit
conversion from string to text is more unexpected than not these days,
and it is better that the user send more direction to the Core / ORM
when passing a raw string as to what direction should be taken.
Core/ORM tutorials have been updated to go more in depth as to how text
is handled.
fixes #2992

The test orm/test_froms.py test_self_referential works with pg8000 now,
so I've opened it up.

:meth:`.Query.select_from` method no longer set up the "from
entity" of the :class:`.Query` object correctly, so that
subsequent :meth:`.Query.filter_by` or :meth:`.Query.join`
calls would fail to check the appropriate "from" entity when
searching for attributes by string name.
fixes #3083