• 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.