adding a propriety ready in the up time of the channel

[vincenzopalazzo]

For now, when a node where we have a channel with it is down, we identify it with a timestamp = 0, that it is invalid.

So, here we are missing the timestamp information, and we are required to the client to keep track of it.

It is not important, for the first release at the end of the month, but it is good to make the life easy to the user