Made Route object dynamic

darcs-hash:20081121144935-58103-1605b29cd002fcbeb33c4b7e71f4ec65e817ec2b
Made Credentials object dynamic, added copy methods to both Credentials and Route objects and handle them consistently in the SIP primitive classes

darcs-hash:20081121165651-58103-965390436a66995df341449884c917dd23650db5