better unit tests on authentication

cleaner way to merge user's attributes from different backends

fix decorator handling the exceptions

slightly cleaner way to handle templates loading

pep8 compliance

small code reorganization ...

* extraction of exception decorator
* extraction of log handling

Update README.rst

increment version number in doc

increment version number

fill ChangeLog

using demo backend as an example ...

the demo backend is far simplier than the ldap backend,
so it's more logic to use it as an implementation example

adding documentation for demo

adding a demo backend

adding documentation for custom js

implementing custom js

better comment in default configuration + add section ...

* better comments in default config about static file serving
* adding section for futur functionality: adding custom js files
  (for auto-fill)

cosmetic change in doc

complete AD backend documentation

adding confirqtion for backends

typo in changelog

ChangeLog at root of repo + log of current devs.

fix some typos

fix unit test on duplicate user exception

adding vim swp file in gitignore

custom error handling for UserDoesntExist, UserAlreadyExists and GroupDoesntExist

typo in comment

pretier and cleaner run_test.sh

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)

turnoff the check for configuration file

extracting screenshots in a separate page