Multiple interest rates on a CPN?

[jacobyavis]

In Shareworks you can store multiples interest rates along with their effective dates on a convertible note.
E.g.
1% interest for the first year
1.5% interest for the second year
2% interest after that

The OCF format does not support this as there's only the one field for interest rate.

[JSv4]

Converted to issue #262