Fix fake boolean params and docs update

This MR provides a workaround for the "boolean" parameters that can't be passed as real booleans in Centreon.

We also log in broker log if parameters are set with now incorrect types: this will help users identify old configs where they used strings "true" or "false".

Plus a global README update/review.

This MR should remain "draft" until the matching changes in French docs are ready (for doc.canopsis.net).

Closes #13 (closed)