Add capabilities to addmin to regenerate the API key of his app

Now the api_key of app can be regenerate. In previous this api-key can't
be regenerate by the web front. To regenerate this api_key you need go
to the edit app page.

See #547
Merge pull request #572 from shingara/features/regenerate_api_key

Add capabilities to addmin to regenerate the API key of his app