Encoding to utf-8 the cluster CSV statistics file output

Small refactoring

Adding missing test data file

Adding tests for proportional missing strategy predictions

Improving locale handling to avoid problems in console logs on Windows

Adding the method to create sources from batch predictions and fields…

… stats

Changing create methods to check origin resources with full=false

Updating version to 1.6.3

Typos and pylint complying changes

Adding retries to the download_dataset method