Recognize brackets, quoted_name in SQL Server schema

Recognize brackets, quoted_name in SQL Server schema

The SQL Server dialect now allows for a database and/or owner name
with a dot inside of it, using brackets explicitly in the string around
the owner and optionally the database name as well.  In addition,
sending the :class:`.quoted_name` construct for the schema name will
not split on the dot and will deliver the full string as the "owner".
:class:`.quoted_name` is also now available from the ``sqlalchemy.sql``
import space.

Change-Id: I77491d63ce47638bd23787d903ccde2f35a9d43d
Fixes: #2626