[FL-1371] New LF-RFID app. Second encounter. (#547)

* File worker: file operations helper.
* Notification app: removed yield
* File worker: write operations, calls to system file widgets
* App ibutton: use file worker
* Lfrfid: generic key loading, add path helper and hex conversion to lib
* FileWorker: plain C verison
* FileWorker: add to lib.mk
* FileWorker: add to C sources, instead of CPP
* Lfrfid: save scene
* App lfrfid: add key scene, saved key menu
* App lfrfid: saved key info scene
* App lfrfid: delete key scene

lib/args/path.h

@@ -0,0 +1,18 @@
+#pragma once
+#include "m-string.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief Extract filename without extension from path.
+ * 
+ * @param path path string
+ * @param filename output filename string. Must be initialized before.
+ */
+void path_extract_filename_no_ext(const char* path, string_t filename);
+
+#ifdef __cplusplus
+}
+#endif