Add property to get the number of a page

app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderActivity.kt

@@ -331,7 +331,7 @@ class ReaderActivity : BaseRxActivity<ReaderPresenter>() {
     fun onPageChanged(page: Page) {
         presenter.onPageChanged(page)
 
-        val pageNumber = page.index + 1
+        val pageNumber = page.number
         val pageCount = page.chapter.pages!!.size
         page_number.text = "$pageNumber/$pageCount"
         if (page_seekbar.rotation != 180f) {

app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderPresenter.kt

@@ -579,7 +579,7 @@ class ReaderPresenter : BasePresenter<ReaderActivity>() {
                     // Build destination file.
                     val ext = MimeTypeMap.getSingleton().getExtensionFromMimeType(mime) ?: "jpg"
                     val filename = DiskUtil.buildValidFilename(
-                            "${manga.title} - ${chapter.name}") + " - ${page.index + 1}.$ext"
+                            "${manga.title} - ${chapter.name}") + " - ${page.number}.$ext"
                     val destFile = File(destDir, filename)
 
                     context.contentResolver.openInputStream(page.uri).use { input ->