Allow aptcacheexport to send data to server

Add an extra parameter so json data can be send to a server via HTTP
POST. Also the FQDN is send to the server together with the package
information.
For manual testing, also add a little HTTP server which is mentioned in
the README.rst.
Merge pull request #3 from TelekomCloud/feature/send-via-http-post

Allow aptcacheexport to send data to server