[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

applications/lfrfid/helpers/key-info.h

@@ -11,4 +11,5 @@ enum class LfrfidKeyType : uint8_t {
 };
 
 const char* lfrfid_key_get_type_string(LfrfidKeyType type);
+bool lfrfid_key_get_string_type(const char* string, LfrfidKeyType* type);
 uint8_t lfrfid_key_get_type_data_count(LfrfidKeyType type);