MatchValueFunction: x10 if match before separator

Encourage matching the first product code in the listing, by multiplying
the value by 10 if the match is before the first slash "/" or round
bracket "(".

Examples:
1. Rebel T2i instead of EOS 550D for "Canon EOS 550D (European EOS Rebel
T2i)"
2. TL240 instead of ST5000 for "LCD Samsung TL240/ST5000"