PublishRoutingServices tool should check if the server used to publish routing services has a valid network analyst license

If the server used for publishing routing services does not have a network analyst license, the PublishRoutingServices tool does not provide a useful error message as evidenced in #14.

Since the PublishRoutingServices tool connects to the server as an administrator, it can perform the license check and provide a better error message.

Thanks to @selsoz for reporting this issue.