Refactor authentication system.

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

See https://github.com/marienfressinaud/FreshRSS/issues/655

app/Controllers/usersController.php

@@ -5,7 +5,7 @@ class FreshRSS_users_Controller extends Minz_ActionController {
 	const BCRYPT_COST = 9;	//Will also have to be computed client side on mobile devices, so do not use a too high cost
 
 	public function firstAction() {
-		if (!$this->view->loginOk) {
+		if (!FreshRSS_Auth::hasAccess()) {
 			Minz_Error::error(
 				403,
 				array('error' => array(_t('access_denied')))