Evolution #269

* Improve the provider invoice management.
* When we enter the same invoice numver as a previous one, we now have
the choice, to change, remove current one or view previous one.
* When importing two time the same file, we now have an error (based on
the md5 of the file).
* Changed the structure of the module to match with the new igestis
core standard. To expose only the public file (js, css, images)