Fix bugs in DBus.
Add short comment to Variant method packing GVariant.
Fix some spelling mistakes and assertions in Variant templates.
Update D-Bus interfaces XML and add signals for maintaining neighbours in neighbourhood.
UniquePtrGVariant is now new class deriving from unique_ptr specialization. Thanks to that, I assured, that g_variant_ref() is called on GVariant instances.
Simplify classes in protocol namespace. Remove code responsible for serialization (both network and GVariant). Also remove field 'address' from Neighbour and 'magic_string' from Announcement.
Protocol::Neighbour serialization was moved here. IP address was added to GVariant dictionary for Neighbour.
Serialization for classes from Protocol name space was moved to Serializable class. Note how serialization of Announcement changed (how magic string is handled).
Updated utilities.hpp (should be committed within 85f604a2c8c06fda646fa795cad333e49bb94795).
Update Neighbourhood due to changes in Serializable, Variant and Protocol.
Extend Serializable and Variant tests.
Small update in UdpMulticastSocket.
Update Makefile.