setup script for itemsets

a few things to consider:
 - the virtual Itemset-Ids will not be the same as wowheads. Which dosn't really matter imho..
 - the Arena-Sets all have their base names. I've to admit, i'm not too fond of the idea to collect 40 prefix-strings and attach them manually. But i see no other option.
 - availability for players is not supported. I dread the thought of crawling through vendor and loot-tables for every .. single .. item!