channeldb: add payments query
channeldb: add payments query

Adds a PaymentsQuery struct, which contains parameters to restrict the
response of QueryPayments, returning a PaymentsQuerySlice with the
payments query result. The behavior of this api is the same as
the QueryInvoices one.

LightningNetwork/lnd,LightningNetwork/lnd,aakselrod/lnd,aakselrod/lnd