Dedupe tweaks

Deduping now behaves differently:

 - If no number supplied while deduping then the whole list is deduped
 - Only deduped what was asked
 - By default each template coming through `facia` now dedupes only the top 5 items.

If an item has been deduped in the past and is within the deduping bounds, it will never show again in further down the list if it appears within the deduping bounds. If an item is outside the deduping bounds then it will always show, deduped in the past or not.

I have also added tests around deduping.