Copying data across years.

[PiotrEsse]

Hi, I think it would be better to improve copying and pasting across years. Now you copy and paste whole year.
2 improvements:

1. copy and paste just income or expenses. Not both. its more flexible
2. copy and paste - adds data not replace (selectable as a option)

[simonwep]

This is a great idea, I figure this would need to be done in a modal (the pasting) to customize it. I'll convert this to an issue :) - #80