maps the absolute position onto the 5 position categories
position categories: early,mid,late,sb,bb - positions start at 0
categories are filled from EARLY to LATE
e.g. 7 players:
0->3(SB); 1->4(BB); 2->0(EARLY); 3->0(EARLY); 4->1(MIDDLE); 5->1(MIDDLE); 6->2(LATE);