fix unit test on duplicate user exception

multiple modification/fix ...

* add display_name parameter for backend
* handle display_name in modify template (lonely groups) and error
  message
* fix bug in modify when user is in only one backend
* remove redondant exception in ad/ldap backend
* fix unit test accordingly
* fix License in AD backend (GPLv3 -> MIT, previously tought of using
  samba4 python library which is GPL, but this module finaly uses
  python-ldap which is MIT compatible)

adding utf-8 char in unit tests for ldap backend

remove trailing spaces

remove useless test

various fix on ssl/tls + tests ...

* making ssl cert check and cert no check works
* adding a test to check if the cafile does exist
* reenable and fix ssl checks on travis

adding various unit tests

reverse because no effect + disable ssl unit test on travis

adding unit test for starttls

fix path to ca

reenable ssl no cert check

test for travis

more logs

greater timeout

fix unit test and fix the way ldap connexion options are handled

adding test for add/delete groups

small reorganization

fix and add unit tests on ldap backend

adding key handling

add unit test for get_user

adding unit test for del user if user don't exist

add unit test for get_groups

fix test on ldap backend

adding methods add_user and del_user ...

* adding add_user
* adding del_user
* adding unit tests
* adding configuration parameters for adding users

adding objectclasses options

implementing search users ...

* adding search
* adding unit tests

adding search template

multiple changes ...

* implemeting recover user attributes
* adding a unit test for unavailable ldap
* adding a parameter timeout to set the ldap timeout connexion

adding unit test for ldap server unavailable

add passing attributes list to backend