Added Couchbase Server Community & Enterprise Casks & removed Couchbase Cask

Hi,

Couchbase Server is now available for OS X in the Community and Enterprise versions, so I've removed the existing Couchbase Cask, and added Couchbase Server Community and Couchbase Server Enterprise Casks at their currently released versions.

The reason I removed the existing Couchbase Cask is due to naming inconsistency (the product is called *Couchbase Server*, the organization itself is *Couchbase*). I hope having two separate Casks is acceptable, and if there is a best practice way to handle 2 different flavors of an application that is preferred over having 2 separate casks, please let me know what that approach is and I'll be happy to make modifications and resubmit my PR.

Cheers!