Admin interface: after deleting a version you return to "Managing my extensions"

What was the cause of the issue?

After the action "deleteExtensionVersion" you get forwarded to the action "index" instead of the action "admin". Furthermore the POSTed extensionKey parameter should also be included in the forward to prevent the user from having to search again for the same key.

Steps to reproduce

• Use the admin interface to search for an extension.
• Delete a version of that extension
• You return to the "Managing my extensions" screen