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)

adding checks for mandatory elements of attributes.yml

begin attributes handling manipulation

unit test + admin roles fix ...

* adding various unit tests
* now admin roles are inherited (ex admin-lv2 is admin -> admin-lv3 is admin
* adding an exception when requesting groups for none existant role

implementing nesting roles

correcting identation on roles.yml configuration file

configuration formatting

adding different type of parameters

adding skeleton to handle form attributes

adding a canevas for role definition

initial commit