Omitting "Field" on ManyToManyField should throw an error

[pa-ching]

If I write something like

class Post(models.Model):
    tags = models.ManyToMany(Tag)

instead of models.ManyToManyField, Django doesn't complain at all. However, any attempts to access (for example) tag_instance.post_set report that there is no such field, and there are probably other things that don't work. This is mainly due to my typing errors, but I've been bitten by this misspelling several times. I guess that I personally forget the Field suffix because ForeignKey doesn't have one. It isn't too big of a deal, but it might be nice for newbies like myself, and Django's error reporting has always been very helpful, either way. Thanks!

[Adrian Holovaty]

(In [2648]) Fixed #1600 -- Renamed ManyToMany to ManyToManyRel so people get a clearer error if they use ManyToMany instead of ManyToManyField