Improve internal codebase

[nyamsprod]

Small improvements

Additions

• Adding missing SensitiveParameter attribute
• Adding Uri::getUsername and Uri::getPassword (both methods return the encoded component). If you need to access the decoded value you should use the UserInfo class instead defined under the Components namespace.
• Adding Ipv6\Converter utility to compress or expand and IPv6 hostname.

Improvement

• Adding an internal cache system to boost UriString::parse when parsing multiple similar domain.

Removal

• Remove BaseUri::getIdnUriString method. The method never got included into an official release). Modifier::getIdnUriString remains.