Docs: SQLAlchemy models do not need an __init__ method

Hi,

In Pyramid documentation and scaffolds all ORM models have an ``__init__`` method which just assigns `name` and `value` to `self.name` and `self.value`.

This method is not needed as SQLAlchemy provides a default constructor which does exactly this (http://docs.sqlalchemy.org/en/rel_0_8/orm/tutorial.html#create-an-instance-of-the-mapped-class)

The practice is kinda ok-ish for a simple model with only two fields, but novice users seem to "scale" the approach linearly to more complex use cases - on stackoverflow I regularly see models like this:

    class Event(Base): 
        __tablename__ = 'event'
        record = Column(Integer, Sequence('event_record_seq'), primary_key=True, nullable=False)
        fileprefix = Column(String)
        date = Column(DateTime, nullable=False)
        eventtype = Column(String(3))
        filename = Column(String)
        memo = Column(String)
        project = Column(String)
     
        def __init__(self, fileprefix, date, eventtype, filename, memo, project):
            self.fileprefix = fileprefix
            self.date = date
            self.eventtype = eventtype
            self.filename = filename
            self.memo = memo
            self.project = project

- which is a serious violation of DRY principle and does not compare favourably with, say, Django ORM.

I removed the `__init__` method from the docs (adding a small explanation) and from the scaffolds.