Remove --upgrade for pip since causes problems.

The latest bundling scripts breaks if --upgrade is there, I don't know
the reason but since we clone the repo each time and install in a clean
virtualenv this option shouldn't be necessary.

Do some code styling and code refactoring.
Use textwrap to have nicer multiple-line strings.
Merge remote-tracking branch 'refs/remotes/ivan/feature/cleanup' into develop
Update README file with up to date docs.
Work in progress...