Refactors the views used to add and delete records.

[Dunedan]

That pull request started as a simple one just trying to improve the implementation of the views a bit, but turned into a larger changeset improving the user experience in a few areas as noted below. The amount of changes might look scary at first sight, but isn't really that bad. Just try it out and enjoy the beauty of the new success and error visualizations.

Notable changes are:

• Refactored views, utilizing more of Djangos features, resulting in simpler code.
• URLs are now the same when initially filling out a form and when editing a submitted form which contained errors.
• Instead of a result page showing the response from the DNS server (which is now logged using Djangos "logging" functionality) the user is now redirected back to the record listing of the current zone when the action was successful or stays on the form page when an error occurred. Proper success/error messages are shown in both cases by utilizing Djangos "messages" functionality.

[jforman]

I have made subsequent checkins to this branch to fix functionality that was broken as a part of your changes. Please test functionality in each pull request (I would highly suggest smaller ones, to make these massive reviews esaier on me).