Fix/downloader not creating folder or cbz file (#676)

* Create manga download dir in case it's missing for cbz downloads

The directory, in which the cbz file should have been saved in, was never created.

* Correctly copy chapter download to final download location

"renameTo" does not include the content of a directory.
Thus, it just created an empty chapter folder int the final download directory

server/src/main/kotlin/suwayomi/tachidesk/manga/impl/util/DirName.kt

@@ -48,6 +48,10 @@ fun getThumbnailDownloadPath(mangaId: Int): String {
     return applicationDirs.thumbnailDownloadsRoot + "/$mangaId"
 }
 
+fun getMangaDownloadDir(mangaId: Int): String {
+    return applicationDirs.mangaDownloadsRoot + "/" + getMangaDir(mangaId)
+}
+
 fun getChapterDownloadPath(mangaId: Int, chapterId: Int): String {
     return applicationDirs.mangaDownloadsRoot + "/" + getChapterDir(mangaId, chapterId)
 }