UCI HAR Summarisation script + CodeBook + ReadMe

This REPO contains a script (run_analysis.R) to summarise original UCI
HAR Smartphone dataset, plus a CodeBook markdown for this summarisaiton,
plus README markdown for showing how script works. Also included (even
if not requested by Coursera Assignment) a sample of the output tidy
dataset (TidyDataSet.txt).
Enjoy!
In this commit I updated CodeBook with some more notes on units of
measure