Allow the name of Google Shared Drive to be used in the storage url

The previous PR only accepts the id of the shared drive, which is not very
memorable.  This commit makes it able to specify the drive by id or by name.

src/duplicacy_gcdstorage.go

@@ -367,6 +367,24 @@ func CreateGCDStorage(tokenFile string, driveID string, storagePath string, thre
 
 	if len(driveID) == 0 {
 		driveID = GCDUserDrive
+	} else {
+		driveList, err := drive.NewTeamdrivesService(service).List().Do()
+		if err != nil {
+			return nil, fmt.Errorf("Failed to look up the drive id: %v", err)
+		}
+
+		found := false
+		for _, teamDrive := range driveList.TeamDrives {
+			if teamDrive.Id == driveID || teamDrive.Name == driveID {
+				driveID = teamDrive.Id
+				found = true
+				break
+			}
+		}
+
+		if !found {
+			return nil, fmt.Errorf("%s is not the id or name of a shared drive", driveID)
+		}
 	}
 
 	storage = &GCDStorage{