Enforced unique Division Names

[mfranchetti]

When creating a new division [ Division::create() ], OBBLM checks to see if the name is already in use and the create fails if so.

1. The error message is simply 'Failed', which gives no useful information to the user about how to rectify the issue.
2. Is there a need for Division names to be unique? Particularly in a multi-league setup, names such as 'Season 1' will likely be in common use. All code should be using the Division ID rather than relying on the name at any point. Would need testing to confirm that this was the case though.