Make $_REQUEST processing independent of sub-calls

- Move HTTPInputData::process() into App::runFrontend()
- Pass $_REQUEST (including processed Input) to every Module method
- Delete $_POST parameters at Module post() calls because of $_REQUEST

src/Module/Register.php

@@ -193,7 +193,7 @@ class Register extends BaseModule
 	 * Extend this method if the module is supposed to process POST requests.
 	 * Doesn't display any content
 	 */
-	protected function post(array $request = [], array $post = [])
+	protected function post(array $request = [])
 	{
 		BaseModule::checkFormSecurityTokenRedirectOnError('/register', 'register');