add data.table support
1.set channel and stain to NA if they are not needed for QA 2.use flowWorkspace:::.getPopStat to avoid rbind operation from getPopStat call to futher speed up
add data.table to depends list
add isChannel flag to getQAStats to eliminate the need of getGate and getData by default
fix a bug in getQAStats.env
fix group outlier detection bug
add qa.get.par to use global  name for the generic id col
strip the name from stats column