Cash Forecaster 0.6

Cash Forecaster allows you to generate a graph and summary of your cash flow over a defined period given an number of user-defined revenues and expenses.

Enhancements
- Ensure that all date fields accept natural language. You should now be able to enter "tomorrow", "today", "6/6", "June 6", etc
Added ability to amortise cash flow. You can now model:
- Discounted cash flows (Can therefore model project cash flows, i.e. NPV)
- Loans
- Cash accounts that accrue interest.
- Can now print forecasted graph of cash flows
- Added export to CSV function.
- Ensured that all dependant fields (Expired, Final occurence) are assessed correctly when opening files
- Changed "Repeats" to "Occurrences" - this should avoid confusion about how the payments are calculated