Utils/Logger: FileTarget implementation

Utils/Logger: Fix routing API ambiguities

Utils/Logger: Completed the target routing and querying API

Utils/Logger: Implement message routing -> logging library is working now
Move 'nil' class into Utils/mpl.hh

Utils/Logger: Documentation
Utils/Logger: Better SENF_LOG_CLASS_AREA integration
Utils/Logger: Fix compile-time config bug for larger configurations

Packets/MPEGDVBBundle: Use senf::Parse_Variant in SNDUPacket

Packets: Move example policies into .dox files
Packets: Implement variant parser

Utils: Implement ErrnoException

Packets: Add parse helpers for private fields
Packets: Rename all SENF_PARSE_ parse helpers to SENF_PARSER_
Packets/MPEGDVBBundle: Fix parsers to make use of the new parse helper features
Add additional Doxygen predefined macros to correctly parse the packet parse helper macros

Packets: Add parse helper unit-test

Utils/Logger: New SENF_LOG_CONF syntax supporting not-yet-declared areas and streams
Utils/Logger: Target baseclass

Logger: Implemented compile-time configuration support

Packets/DefaultBundle: Implement IpV6Packet, IpV6Extensions and UDPPacket's finalize()

Packets: Implemnet generic assignment of boost::optional's to parsers
Packets: Fix <n>_offset field definition in BOOST_PACKET_PARSER_DEFINE_FIELDS
Packets: Implement PacketTypeMixin::key() helper
Packets: Clarify documentation regiarding valid()/in-valid() packets
Packets/DefaultBundle: Implement EthernetPacket, EthVLanPacket and IpV4Packet's finalize()