- revert the 4 missing tests, e.g. proxy test from commit 20468f5b
- add virtual host name `test.localhost` to embedded jetty server
  (JUnit Tests) since localhost and IP-Addresses are no longer
  supported by the proxy and use this address inside proxy `src`
- add `test-localhost` support for the docker tests. To support
  this the docker hostname need to be set to test.localhost by:
  `--hostname=test.localhost` (only for the docker tests)
- proxy: add file format support for PDF
- proxy: add error messages on "bad request" response
- proxy: remove dead code
- old proxy: add error messages on "bad request" response
- fix incorrect README link to docs
- add `HTTP_PROXY_READ_TIMEOUT` option -- close #240