Allow duplicate categories if the point is the last one in the chart

[davestaab]

Currently if you add a duplicate category that's contiguous to a point that's the same category the new one "wins" and the older one if deleted.

This proactively removed duplicates and allows you to intuitively "edit" the time line.

However there's a use case where you want two entries of the same category. When you're finishing out the day you stop work at some point. You currently have to use a different category at the very end to create a line for your last category. It would be nice to just put a second point down for that last time entry.