Fix: several problems that an XML + XSLT weg page cannot be correctly captured.
Fix: several problems that an XML + XSLT weg page cannot be correctly captured.

- The document is not regarded as an HTML if there is no <body> element
- Nodes before or after the <body> node are ignored
- Create a linefeed before and after the auto-generated <meta charset="UTF-8">
- Optimizes sbContentSaver.saveDocumentInternal()

danny0838/firefox-scrapbook,danny0838/firefox-scrapbook