Assignment V3.0.2. CodeBook.md format ajusted.
Abbreviated four long explanations to make sure each explation occupies only one row.
FreqBodyAccJerkMagMean: Frequency -> Freq
TimeBodyAccJerkMagStd: Deviation -> Dev
FreqBodyAccJerkMagStd: Frequency -> Freq
FreqBodyGyroJerkMagStd: Frequency -> Freq