Categorizer names can be non-unique

[khatchad]

Categorizers could conceivably have the same name. Why is this field unique.

Imperative-DL-Study-Web-App/ponder/models.py

Line 63 in 9531da8

name = models.CharField(unique=True, max_length=254)

[mZneit]

In the production database, this field is unique. If we change it to non-unique and do migrations, we'll get into error if we populate the data from the production db.

[mZneit]

Similarly for #145.