* Fix `Uri::__toString` for network path references, e.g. `//example.org`.
* Fix missing lowercase normalization for host.
* Fix handling of URI components in case they are `'0'` in a lot of places,
  e.g. as a user info password.
* Fix `Uri::withAddedHeader` to correctly merge headers with different case.
* Fix trimming of header values in `Uri::withAddedHeader`. Header values may
  be surrounded by whitespace which should be ignored according to RFC 7230
  Section 3.2.4. This does not apply to header names.
* Fix `Uri::withAddedHeader` with an array of header values.
* Fix `Uri::resolve` when base path has no slash and handling of fragment.
* Fix handling of encoding in `Uri::with(out)QueryValue` so one can pass the
  key/value both in encoded as well as decoded form to those methods. This is
  consistent with withPath, withQuery etc.
* Fix `ServerRequest::withoutAttribute` when attribute value is null.