Updated Doxyfile.
Fixed doxygen ref.
Using PlantUML integration of doxygen.
Moved socket interfaces into an own installable directory.
Updated required doxygen version to use integrated PlantUML support.
Removed connect function from connection_interface.
Refactored typedefs to usings.
Renamed namespace rest to hutzn.
Renamed rest.?pp to hutzn.?pp.
connection::receive: The buffer size has to get reduced again in any case.
Many comments on socket interfaces.
More documentation of the socket interfaces.
Removed compiler flag -Wno-sign-conversion.
Fixed include.
Commented and refactored socket utilities.
Replaced two unions.
Added override flags to the virtual functions, that implementing the interface.
Fixed include guards. Removed unnecessary includes.
Reduced explicit :: to a minimum.
More constness. Some refactoring.