Feat calculate percentile#22

Percentile gets now calculated as Tobias wants.

Currently, the color is green, maybe we should change it to black but the statistical values can already not be distinguished that well...

Also, I extended the test set for the math file and changed the quantile calculation to the one we also learned in our statistics class (^= Wikipedias "Method 1", the article is also linked in the jsdoc of math.js).

Additionally, I added missing jsdoc comments to the constants file.