Added new kw argument to :meth:`.EnvironmentContext.configure`

Added new kw argument to :meth:`.EnvironmentContext.configure`
``include_object``.  This is a more flexible version of the
``include_symbol`` argument which allows filtering of columns as well as tables
from the autogenerate process,
and in the future will also work for types, constraints and
other constructs.  The fully constructed schema object is passed,
including its name and type as well as a flag indicating if the object
is from the local application metadata or is reflected.