Revert budget balancing

[jantman]

Revert most of PR #127 that was opened to fix #117, end of pay period budget balancing.

I think that solution was overly complex and completely missed the point. There's really no need to balance each budget individually, and that actually does the wrong thing for pay periods that have many budgets with negative remaining values (i.e. periodic budgets with $0 budgeted but some amount spent) but still have an overall spend significantly less than income.

So, fixes for this, I think...

• revert most of PR Issues/117 #127
• for payperiods in the past, always calculate based on the actual spent amount, not the allocated amount
• for balancing of payperiods, all that's needed is a manual transfer between periodic and standing, of the payperiod overall remaining amount