Lack of support for multiple occurances of year token in license header

[splatch]

Using a maven plugin I found out that version 2.24.0 rely on singe occurrence of year token. Sadly license header I deal with have two lines where $YEAR should be inserted. This seems to be unsupported by the way how license step is being made.

[nedtwigg]

Happy to take a PR that supports placing the year in multiple places.