Implement model relationships

[onyb]

Django-style many-to-many relationships is a highly desirable feature. There might be some refactoring involved in reobject.manager.Manager.

class Publication(models.Model):
    def __init__(self, title):
        self.title = title

class Article(Model):
    def __init__(self, headline):
        self.publications = models.ManyToManyField(Publication)
        self.headline = headline

ReObject should allow the following usages:

• a.publications.all()
• p.article_set.all()
• a.publications.create(..)
• a.publications.add(p)
• Article.objects.filter(publications__title__startswith="Science")
• Publication.objects.filter(article__headline__startswith="NASA")