Add stepwiseqtlQuoc.R

This is the clean version of stepwiseqtlX with more comments and 1 obsolete function deleted. We can take stepwiseqtlX out of the repo and only work on this file for the code merge. 
4 main functions: countqtltermsQuoc, calcQuoc.penalties, stepwiseqtlQuocv12514, calc.plodQuoc.