Getting-and-cleaning-data

1. If not existing yet, download the file and extract it.
2. Create datasets for each .txt contained in the zip folder, assigning the variable names.
3. Merge the datasets created, obtaining a large one which is built up merging X files, Y files, subject files.
4. Extract mean and standard deviation for each measurement.
5. Label the data set with descriptive variable name taken from the code book.
6. Create a second data set with the average of each variable for each activity and each subject.

The result is stored in "tidy_mean.txt"