When reading raw data every columns were parse as character.
Now data type is preserved when parsing.

A parenthesis was missing in the call to source() in the Set-up script
section of the manual.

- Not tracked
- Test case for extraction script

If any column is empty script with now halt with a proper error message.
No more empty workbook will be produced.

Do not restrict input to UTF-8 format.

Avoid unexpected coercicion by sapply().

- Break the logic into adequately named functions
- Add documentation using Roxygen syntax

This allow the developer to:
- Take snapshot of data/processed/ directory
- Test if current excel workbook holding data and metadata correspond
to the last snapshot

Snapshots are stored as .Rdata files in scripts/tests/
The scripts/tests/ directory upon download by the student

Remove results file with dot as name separator
Cleaned data is now saved in data/cleaned/

readline() was behaving differently between local and url source.
In url case calling readline did not pause script execution. User directly ended up
in input validation while loop.

Functions and previous metadata extractrion.