Alias Storage

[sargon]

With upcoming alfred support in gluon the need for a central alias information list decreases. Since we won't have any persistent alias informations at some time in the feature, hence any node going offline will immediately vanish from the map.

We should have some persistent store, where we archive the client meta informations for some time. So the client will be visible for maybe a day or two in the map even if connection broke or it is turned off.

[tcatm]

I think I've implemented just that in the persistence branch. I'm going to merge it to master in a few days if it works reasonably well.