Add the ability to duplicate a segment

[matthewelwell]

Add an option against each segment in a project to duplicate the segment. The user should be prompted to provide a name for the duplicated segment but nothing else - all the other data for the segment should be coped from the segment being duplicated.

Note that we only want to duplicate the segment itself, not any segment overrides.

If the segment is a feature-specific segment, the duplicated segment should also be a feature-specific segment.

[sbhrwlr]

I’ve created a PR addressing this issue. PR