Extract first image into the blog image during BlogML import

[simonech]

trafficstars

Now when there is post via metablogapi, the first picture is extracted and put into the "blog image" filed. It would be cool to do the same during the import from BlogML

[Shazwazza]

This PR has been merged so closing this issue

[Shazwazza]

Have re-opened this since the PR addresses importing an image if the image exists in the attachments collection but if we want to extract the image based on the first image tag found in the markup, than that's a different story.