new trigger count thresholds suggestion

rationale: 
in general I think if the study lifetime was longer, we should have made the thresholds bigger to make them resistant to noise and temporary behaviors but since we want the thresholds to happen in the middle of the experiment, we have to keep them fairly small but remember that it's usually the frequency that matters, e.g. youtubecountthreshold = 2 actually means 2 times in a few days. 

*close tab and new tab: I made them larger because they happen more frequently.
*download: 2 downloads is not many as people download files day to day, 4 is a slightly larger and filters occasional downloads
*youtube: we suggest youtube download for youtube. So it's better to filter people that occasionally go to youtube. Everyone occasionally goes to youtube.