progress page when sending a payment shows "loading network..."

[Roasbeef]

When a user sends a payment, and it takes a few seconds, then they're presented with the current network loading screen. The text states: "loading network...", which is out of context as the network has already been "loaded", and we're now routing a payment through the network. So it's a matter of using distinct copy when we transition to the loading page due to sending a a payment. Some suggestions for copy:

• "sending payment..."
• "routing payment..."