Creates and returns a deep copy of the Header. This methods must ensure a deep copy of the Header, so that when a message is cloned the Header can be modified without effecting the original Header in the message. This provides useful functionality for proxying Requests and Responses, for example:
- Recieve a message.
- Create a deep clone of the message and headers.
- Modify necessary headers.
- Proxy the message using the send methods on the SipProvider.
This method overrides the clone method in java.lang.Object.
@return a deep copy of Header