Seller escrow release times

[grunch]

We need to calculate the average time between the buyer take the order and the seller release the funds.

We can show this number when the bot publishes the order.

In order to not penalize the seller if the buyer takes much time sending the fiat money, we will need to add a new command to the user to indicate that the fiat was sent, since that moment we start to count the time again to have the seller's average