Increase pressure on user photo

Related to issue #363

- Add a photo field on the registration form thanks to a new module "Registration with picture" (https://drupal.org/project/reg_with_pic).
- On user profile page, display a small text instead of the default picture.
- Sends a note on each login to remind about the photo.

The photo field on the registration form appears at the end of the form, which is not so fancy, on the module web page they say we can use "Registration Picture Field Weight" to fix that, but where is it ?
Set this field required on registration forrm is also possible with this module.
Do we need to email from time to time ?