epubview: Fix epub books always opening on page 1

The page/chapter read count is not honored for epubs and the ebook is reopened on the first page instead.

The epub view's slider's range is set to be between 1.0 and X where X is the number of pages in the document, after the document has been loaded.

The default range being between is between 0.0 and 1.0, when the range is set after loading the file, a "value-change" signal will be sent. This signal will be received and a new "1" value written as the current page to disk, before the saved page is read.

Closes: #11 (closed)