Function open_ledger 

fn open_ledger(
    ledger: Ledger,
    consent: &Consent,
) -> (Ledger, usize, BTreeSet<String>)

The budgets’ file as an agent may see it: the budgets, their lines and their recurring payments kept from agents taken out, a line tied to a closed project too; reserves only while things outside projects are open. Returns it, how many budgets and lines were left out, and the labels of those lines (what the money watch would name).