adding loading roles and attributes

begin implementation of the main application

more complete ini conf file ...

adding necessary parameters for backends

rename main class

adding get_attributes

better unit tests

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)

better checks for attributes

adding checks for mandatory elements of attributes.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

enable coverall.io

Update README.rst

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 various methods: ...

* get_groups (get_groups of a role)
* is_admin (determine if ldapcherry admin)
* get_backends (get list of role backends)

better comments and slight improvement in perf

more complex unit test for get_roles

misc role

adding a test for get_roles

fix in get_roles

implementing roles resolution from list of groups

implementing nesting roles

fixing typos in role files

adding an exception for failures to open role file

adding missing dependancy PyYAML

handling exception if a role key is duplicated

fix on unit tests for roles

adding test cases and reworking test env

correcting identation on roles.yml configuration file

adding loading of the roles yaml file