gossip_cyclon: minor docu fixes
cyclon: rm old cyclon settings from scalaris.cfg
gossip_load: move value extraction to callback module
gossip: remove value extraction functions/messages (get_values...)

Value extraction (get_values... messages) is very specific to the callback module
and should therefore be implemented in the api of the given callback module, not
the gossip module.
gossip_vivaldi: add skeleton implementing gossip_beh
gossip_vivaldi: add settings to scalaris.cfg
gossip_vivaldi: implement init()
gossip_cyclon: use half a trigger interval for manual triggers
wip vivaldi select_data