Add support to ``FETCH {FIRST | NEXT} [ count ] {ROW | ROWS}
 {ONLY | WITH TIES}`` in the select for the supported backends,
currently PostgreSQL, Oracle and MSSQL.

Fixes: #5576
Change-Id: Ibb5871a457c0555f82b37e354e7787d15575f1f7

Fixed bug where an error was not raised for lower-case
:func:`_column` added to lower-case :func:`_table` object. This now raises
:class:`_exc.ArgumentError` which has always been the case for
upper-case :class:`_schema.Column` and :class:`_schema.Table`.

Fixes: #5618
Change-Id: Ifcbdf27c022fd2996a5b99559df71fc1c1e0f19c

Fixed bug where an UPDATE statement against a JOIN using MySQL multi-table
format would fail to include the table prefix for the target table if the
statement had no WHERE clause, as only the WHERE clause were scanned to
detect a "multi table update" at that particular point.  The target
is now also scanned if it's a JOIN to get the leftmost table as the
primary table and the additional entries as additional FROM entries.

Fixes: #5617
Change-Id: I26d74afebe06e28af28acf960258f170a1627823

Change-Id: Ibcb0da3166b94aa58fa92d544c3e5cf75844546e

It's better, the majority of these changes look more readable to me.
also found some docstrings that had formatting / quoting issues.

Change-Id: I582a45fde3a5648b2f36bab96bad56881321899b

The :meth:`_sql.Join.alias` method is deprecated and will be removed in
SQLAlchemy 2.0.   An explicit select + subquery, or aliasing of the inner
tables, should be used instead.

Fixes: #5010
Change-Id: Ic913afc31f0d70b0605f9a7af2742a0de1f9ad19

This WIP is part of the final push for 1.4's docs
to fully "2.0-ize" what we can, and have it all ready.

So far this includes a rewrite of the 2.0 migration,
set up for the 1.4 /2.0 docs style, and a total redesign
of the index page using a new flex layout in zzzeeksphinx.

It also reworks some of the API reference sections
to have more subheaders.   zzzeeksphinx is also enhanced
to provide automatic summaries for all api doc section.

Change-Id: I01d360cb9c8749520246b96ee6496143c6037918

For most from_self() tests, move them into
test/orm/test_deprecated.py and replace the existing
test with one that uses aliased() plus a subquery.
This then revealed a few more issues.

Related items:

* Added slice() method to GenerativeSelect, to match that
  of orm.Query and to make possible migration of one of the
  from_self() tests.  moved the utility functions used for this
  from orm/util into sql/util.

* repairs a caching issue related to subqueryload
  where information being derived from the cached path info
  was mixing up with query information based on the per-query
  state, specifically an AliasedClass that is per query.

* for the above issue, it seemed like path_registry maybe
  had to change so that it represents AliasedClass objects
  as their cache key rather than on identity, but it wasn't
  needed.  still seems like it would be more correct.

* enhances the error message raised by coercions for a case
  such as when an AliasedClass holds onto a select() object
  and not a subquery(); will name the original and resolved
  object for clarity  (although how is AliasedClass able to
  accept a Select() object in the first place?)

* Added _set_propagate_attrs() to Query so that again if
  it's passed to AliasedClass, it doesn't raise an error
  during coercion, but again maybe that should also be
  rejected up front

Fixes: #5368
Change-Id: I5912aa611d899acc87a75eb5ee9f95990592f210