Merge thread prefixes (fix after upgrade from mystics to 3.7)

[Alfa1]

Before vbulletin 3.7 I used this hack: Thread Prefixes to have this functionality. Since vbulletin 3.7 thread prefixes are built into vbulletin.
I used this hack to import my thread prefixes into vb 3.7: Thread Prefixes upgrade from Mystics to 3.7

This hack created one prefixes set per forum, because vbulletin 3.7 introduced prefixes sets. This means that I now have 46 almost identical sets of prefixes. Each set contains between 10 and 25 prefixes. Most sets and most prefixes are almost identical. I would like to merge many thread prefixes and sets, so that I just have a few different prefixes sets left. But I do not want to loose prefixes on the thousands of threads that have been categorized with them.

As far as I understand this would be a simple script to code. I may be wrong. Either way; it will be very helpful to many admins and safe loads of work.