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/LegacyModule.php

@@ -73,9 +73,9 @@ class LegacyModule extends BaseModule
 		return $this->runModuleFunction('content');
 	}
 
-	protected function post(array $request = [], array $post = [])
+	protected function post(array $request = [])
 	{
-		parent::post($post);
+		parent::post($request);
 
 		$this->runModuleFunction('post');
 	}