#357 Post-Python 3: Duplicate Award Category name can be created

[Ahasuerus]

A duplicate Award Category name can be created under some circumstances. The submission creation logic in edit/submitnewawardcat.py prevents editors from creating a submission with a pre-existing award category name (within this award type.) However, neither the submission review code nor the filer checks for duplicate category names within the same award type. This means that an editor can create two identical Add Award Category submissions and a moderator can approve them, which will result in two different award categories with the same category name existing for the same award type.