Rename from RsDisc to more descriptive RsGossipDiscovery
Keep full retrocompatibility suggesting usage of RsGossipDiscovery
Add capability to send and receive full RetroShare invitation
Emit event when receiving a full invitation
Start using new debug utilities
Use enum class instead of defines and constant where appropriate
This should bit by bit substitute RsNotify which would be very difficult
to support properly in JSON API.
The new system is much simpler to use also from the C++ side of the
moon.
BroadcastDiscovery take advantage of the new system to notify about new
non friend peer discovered, tested successfully also in JSON API.
