Remove redundant external links section

[bdamokos]

(Possibly related to bug #352)

When you create a PDF there is an automatically generated external sources section added to the PDF and there is usually one already part of the original article. I believe the original "External links" section of the article should be stripped and its contents moved to the generated section in its entirety (not just the links themselves, but the link aliases as well).

If this function is enabled, it should have a localised list of the sections to be moved in their entirety to the auto-generated list of links (including the "References" sections that become empty after all the footnotes have been removed from them).

[volker]

The article http://en.wikipedia.org/wiki/The_Chorus_(2004_film) contains both a reference list and external links section - this seems like a good example for the above mentioned issue