Add tooltip to HTML

Hello Nicholas,

This is a first setup for adding tooltip support (see this issue: https://github.com/akeeba/fof/issues/338).

TODO:

1 It also has to be added to line 1196 of fof/render/strapper.php but I wasn't sure yet how to do this.
2 The tooltip has to be triggered via JavaScript, as explained in http://getbootstrap.com/2.3.2/javascript.html#tooltips. I suggest adding `$('.f0f-tooltip').tooltip({placement: 'top'});`. Either to Akeeba Strapper or F0F.

What do you think?