better example for ldap backend

adding misc

better code example

adding small example for backend ldap

small debug script for class LdapCherry

change backend key name in attributes + methods ...

* adding get_backends
* adding get_selfattributes (attributes users can change themselves)
* adding unit tests
* rename backend-attributes -> bakends (for homogeneity with role.yml)

begin attributes handling manipulation

add methods for class Roles + unit tests ...

* adding get_allroles (list all available roles)
* adding get_display_name (get display name of a role)
* add various unit tests

more complex unit test for get_roles

misc role

implementing nesting roles