Bug4981 confirm ban user

Apologies if I need to rebase AGAIN - I have done so as far as local copies are concerned, and I have pushed, but github apparently disagrees?? I am not really coping with the new repository layout, sigh.

ANYWAY: issues I am aware of:
* I appear to have introduced some stray spaces, which I should probably get rid of for neatness' sake...
* the non-jquery version (as used on e.g. user profiles) seems to take MUCH longer than the jquery version. I assume that is why we are switching to jquery...?
* I would rather the text were more specific ("Are you sure you wish to [ban/unban] this [user/community]?", but I can't see any way to do that that doesn't involve LOTS more lines -- thoughts on preference?

Cheers!