Fix for #1950: make delete_zone an API request. 

next: only offer the option from org_management.

![image](https://cloud.githubusercontent.com/assets/4072455/2686530/ab959e90-c20b-11e3-92a1-30e9c33a2dd2.png)

Changes:

* Move code into `api_*.py`
* Wrap request in `doRequest`
* Return `JsonResponseMessage*` objects, like a good api view should.

Testing:

* Tested the code works from the `zone_management` page.
* Then deleted the option--this should only be available through org management!