English translation of existing comments(and variables) and add some more within:
	- lib/boostrap.php
	- lib/DbConnection.php
	- app/controllers/Controller.php
	- app/controllers/ControllerInterface.php
	- app/models/Model.php
	- app/models/Company.php

Minor indentation changes in lib/Router.php

Files and Class Names(when required) renamed:
	- ConnexionBdd.php > DbConnection.php
	- Entreprise.php   > Company.php
	- acceuil.php      > welcome.php
	- listeEntreprises > companiesList.php

Add Tree view in README.md
URL Rewriting update (.htaccess)
 - URLs no longer need a "/" at the end
 - Two first parameters(controller and action) must be alphabetical, and the last one alphanumeric
 - URLs are rewritten only when containing  1 to 3 parameters (No parameter is Router default behaviour)

Model class is made abstract because it provides services and should not be instantiated.
Minor English grammar correction.

Add DbConnection::__clone() with private scope to neutralise database connection cloning.