add extra_principle_payments for monthly_payment_schedule

[bowzoo]

No description provided.

[alextz]

I must deal with unexpected extra principle payments during the life of a loan, so simply instantiated a new Mortgage when a payment has extra principle using this:

m is the current Mortgage

m = mortgage.Mortgage(rate, m.loan_months() - 1, max(0, m.amount() - list(m.monthly_payment_schedule())[0][0] - extra_principle_payment), payment = m.monthly_payment())

And, the __init__ for Mortgage allows setting the monthly payment like this:

    def __init__(self, interest, months, amount, payment = None):
        self._interest = float(interest)  
        self._months = max(1, int(months))
        self._amount = dollar(amount)
        if  not payment :                              
            payment     = float(self.amount()) * self.rate() / (float(MONTHS_IN_YEAR) * (1.-(1./self.month_growth()) ** self.loan_months()))                                                                       
        self._payment   = dollar(payment, round=decimal.ROUND_CEILING)