cmd/syncthing: Emit new RemoteDownloadProgress event to track remote download progress

Without this the summary service doesn't know to recalculate completion
percentage for remote devices when DownloadProgress messages come in.
That means that completion percentage isn't updated in the GUI while
transfers of large files are ongoing. With this change, it updates
correctly.

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3144

lib/events/events.go

@@ -36,6 +36,7 @@ const (
 	FolderRejected
 	ConfigSaved
 	DownloadProgress
+	RemoteDownloadProgress
 	FolderSummary
 	FolderCompletion
 	FolderErrors
@@ -80,6 +81,8 @@ func (t EventType) String() string {
 		return "ConfigSaved"
 	case DownloadProgress:
 		return "DownloadProgress"
+	case RemoteDownloadProgress:
+		return "RemoteDownloadProgress"
 	case FolderSummary:
 		return "FolderSummary"
 	case FolderCompletion: