API: new procedure 'removeAllFiles' and contract change for 'createFile'

app/check_setup.php

@@ -38,3 +38,15 @@ if (! is_writable('data')) {
 if (ini_get('arg_separator.output') === '&') {
     ini_set('arg_separator.output', '&');
 }
+
+// Prepare folder for uploaded files
+if (! is_dir(FILES_DIR)) {
+    if (! mkdir(FILES_DIR, 0755, true)) {
+        die('Unable to create the upload directory: "'.FILES_DIR.'"');
+    }
+}
+
+// Check permissions for files folder
+if (! is_writable(FILES_DIR)) {
+    die('The directory "'.FILES_DIR.'" must be writeable by your webserver user');
+}