Due to peer reconnects when restarting the Management service,
there are lots of SaveStore operations to update peer status.
Store.SavePeerStatus stores peer status separately and the
FileStore implementation stores it in memory.
Added DNS update protocol message
Added sync to clients
Update nameserver API with new fields
Added default NS groups
Added new dns-name flag for the management service append to peer DNS label
This PR simplifies Store and FileStore
by keeping just the Get and Save account methods.
The AccountManager operates mostly around
a single account, so it makes sense to fetch
the whole account object from the store.
