'cabal init' command should allow for multiple entries in the Category field

[byorgey]

The .cabal format allows multiple categories (e.g. Data, Network, Math, etc.) to be listed in the Category field, but the 'cabal init' interactive mode only lets the user choose a single category. It would be nice to allow the user to choose multiple categories.

[gwern]

Can't say I'm too eager to see this feature; I've been less than impressed with peoples' general ability to finely categorize their packages (as opposed to throwing them in half the categories and making up new ones while they're at it).

[byorgey]

Fair enough, someone requested this feature so I made a ticket for it. But it's definitely worth having a discussion on what style we want to encourage, since that's part of the goal of cabal init. If we want to encourage everyone to have just one category, then marking this "won't fix" is fine by me.

[duncan]

We could let people know it is possible but gently discourage it by printing a message to let users know that they can add more categories by editing the .cabal file.

[kosmikus]

Should probably be re-evaluated wrt tagging in Hackage 2.