Swap the Services_oEmbed wrapper in oEmbedHelper out for doing it ourselves...

Swap the Services_oEmbed wrapper in oEmbedHelper out for doing it ourselves...
- workaround for providers that are skimpy on their data, such as missing width/height or thumbnail_width/thumbnail_height
- workaround for YFrog listing "image" instead of "photo" type
- generally more lax about formatting: if it comes back and looks kinda ok, we'll take it.
- discovery uses system HTML parser, should be more robust if the links include things like ampersands with proper HTML-level escaping