Working on the separation of accrual and deferral
Merge branch 'master' into Development
Separation of calculation of tests and accrual of interest from actual payments.
Prepared input. Waterfall doesn't use it yet
Relates to #172
Separation of calculation of tests and accrual of interest from actual payments.

Fixed input. Waterfall doesn't use it yet
Relates to #172
Added security checks on input