Utils: Rename SafeBool to safe_bool (hmm ...)

Make all include path's relative
Add 'senf/Packets.hh', 'senf/PPI.hh' and 'senf/Socket.hh'

Socket/Protocols/Inet: Remove not implemented  async resolv constructors (in favor of a later non-member implementation)
Socket/Protocols/Inet: More detailed exceptions thrown by INet4Address / INet6Address

Socket/Protocols/INet: Implement INet6Network

Socket/Protocols/INet: More complete CheckINet6Address documentation

Socket/Protocols/INet: Add optional resolve-type argument to INet6 adressing classes to support IpV4 mapped addresses
Socket/Protocols/INet: removed obsolte INet6SocketAddress constructor

Socket/Protocols/Inet: Update INet6SocketAddress syntax to support hostnames and correct zone-id syntax