Expose if a payment had its fees auto accepted

[danielgranhao]

As part of dealing with #602, we decided to auto-accept fees when they are below a certain threshold and otherwise ask the user to accept them.

When fees go down before the user accepts the new fees, they are auto-accepted if they go below the threshold again, which might be confusing for the user.

It would be helpful to expose a field indicating if a payment had its fees auto-accepted.