support for optional postal addresses

[vohmar]

since 2nd of January 2017 .ee registry does not collect postal aadresses of the domain contacts any more. For this addr element was made optional. But leaving postal address fields empty in web-client will result in schema errors as client tries to send empty addr element fields to the server that is invalid.

The client should leave out all the elements that do not have value from the generated xml request

[vohmar]

the asterisks should be dropped from behind postal address fields

[artur-intech]

#17