Fixes #2623: several fixes:

Disable menu for [..],
Refresh file list after delete,
Copy destination can be a directory,
Prevent copy/paste into the same directory,
Enabled renaming of directories and files without extension,
Removed delete menu option for directories,
Several simulator filesystem functions improved

radio/src/targets/simu/simpgmspace.cpp

@@ -929,14 +929,24 @@ FRESULT f_mkdir (const TCHAR*)
   return FR_OK;
 }
 
-FRESULT f_unlink (const TCHAR*)
+FRESULT f_unlink (const TCHAR* name)
 {
+  char *path = convertSimuPath(name);
+  if (unlink(path)) {
+    TRACE("f_unlink(%s) = error %d (%s)", path, errno, strerror(errno));
+    return FR_INVALID_NAME;
+  }
+  TRACE("f_unlink(%s) = OK", path);
   return FR_OK;
 }
 
 FRESULT f_rename(const TCHAR *oldname, const TCHAR *newname)
 {
-  TRACE("f_rename(%s, %s)", oldname, newname);
+  if ( rename(oldname, newname) < 0) {
+    TRACE("f_rename(%s, %s) = error %d (%s)", oldname, newname, errno, strerror(errno));
+    return FR_INVALID_NAME;
+  }
+  TRACE("f_rename(%s, %s) = OK", oldname, newname);
   return FR_OK;
 }
 
@@ -966,7 +976,12 @@ int f_printf (FIL *fil, const TCHAR * format, ...)
 
 FRESULT f_getcwd (TCHAR *path, UINT sz_path)
 {
-  strcpy(path, ".");
+  // remove simuSdDirectory from the cwd
+  char * cwd = get_current_dir_name();
+  std::string c(cwd + strlen(simuSdDirectory));
+  free(cwd);
+  strcpy(path, c.c_str());
+  TRACE("f_getcwd() = %s", path);
   return FR_OK;
 }