Allow saving to Remarkable Root; Resolves #6

[artes-dev]

This allows calling the Synchronizer with rRootFolderName = false in order to save to the root of the Remarkable, instead of under a sync folder: let sync = new Synchronizer(rOneTimeCode, gdFolderSearchParams, false, syncMode);

This also resolves #6; the Google Drive folder ceases to appear under the Remarkable sync folder, only its contents are synced.