Accounts which have no budget goals within the report period are now
grouped under <unbudgeted> - not just accounts with no budget goals ever.
Haddocks have been clarified, especially for budgetRollup. In some
ways things are much clearer without this feature, but it remains
enabled by default for now.
Budgets were restricted to a single interval in 1.9, but this was
a mistake. This restores the 1.5 behaviour, where a budget can be built
up from multiple periodic transactions with different intervals.
