Refactor authentication system.

Big work, not finished. A lot of features have been removed.

See https://github.com/marienfressinaud/FreshRSS/issues/655
Introduce FreshRSS_Auth::hasAccess('admin')

Replace Minz_Configuration::isAdmin($user). FreshRSS_Auth::hasAccess() could
be extended to others scopes later.

See https://github.com/marienfressinaud/FreshRSS/issues/655
Authentication system moved + Persona comes back!

AuthController is dedicated to auhentication.
Persona is back, greater than ever!

See https://github.com/marienfressinaud/FreshRSS/issues/655
Reset auth system comes back!

It has moved to authController.
Merge branch 'refactor-authentication' into dev