Link relationship (rel attribute) on "advanced" tab for links

[tigris]

I have attached a patch that implements the rel="" attribute for link tags.

This may be somewhat a dupe of ticket:2145, but I notice Ben listed multiple feature requests in his ticket, which is shunned.

In any case, the patch is a pretty simple one, however it halves the space in the advanced tab for the "styles" text box.

I'm also unfamiliar with the code base, so not sure if I've missed anything, such as unit tests etc.

[tigris]

patch implementing rel attribute in links

[wwalc]

Duplicate of #4890 (FCKeditor 2.x is no longer maintained, we'll fix it in CKEditor 3.x).