jQuery 1.9 compatibility changes

these changes should make Products.CMFPlone 4.3 mostly compatible with jQuery 1.9 (necessary, to use Bootstrap 3 with Plone 4.3)

the changes should be quite safe, but require jQuery 1.7+ in place. therefore the minimum plone.app.jquery version declaration insetup.py (@timo, i think we should have this version fix in here. otherwise, the javascript won't work).

@garbas @davisagli @tisto may you can have a quick look at it?

i'm going to cherry pick this for the master branch.