Wizard and PresetUpdater changes

updater:
- Sync downloads also missing thumbnails.
- Copying of downloaded resources (perform_updates) also downloads missing ones (new vendor or installing vendor with added printers ).
- This copy&download shows progress dialog now.
- Fix of crash when installing new vendor (not in rsrc dir)
Wizard:
- Cancel updater sync when starting wizard to avoid multiple downloads.
- Load thumbnails from cache dir (downloaded by updater sync).
Preset:
- Profiles now has settable name of thumbnail. If not specified, name + _thubnail.png is used (as it was before).

src/slic3r/GUI/GUI_App.cpp

@@ -2999,6 +2999,8 @@ bool GUI_App::run_wizard(ConfigWizard::RunReason reason, ConfigWizard::StartPage
     wxCHECK_MSG(mainframe != nullptr, false, "Internal error: Main frame not created / null");
 
     if (reason == ConfigWizard::RR_USER) {
+        // Cancel sync before starting wizard to prevent two downloads at same time
+        preset_updater->cancel_sync();
         if (preset_updater->config_update(app_config->orig_version(), PresetUpdater::UpdateParams::FORCED_BEFORE_WIZARD) == PresetUpdater::R_ALL_CANCELED)
             return false;
     }