Run pre transformation option before extract metadata

[andremacola]

I think this will be a good option, because sometimes we can fix or add some markup to the html to facilitate metadata extraction.

Ex: add a date markup to extract date.

[ndaidong]

Yes, this is a good idea. Let me check the logic here.

[ndaidong]

With the current version, there is a challenge here: we need the url to find related transformations.
Currently we still rely on the metadata to determine the best url for article.