Display helpful button tooltips

[Spengreb]

I've added tooltips to a variety of buttons in LUPPP to describe their usage to a complete noob.

This was the first code change I tried to make to LUPPP and forgot to push it to upstream, I hope the descriptions are correct for each element. I read as much as I could to understand each one but honestly some of there are still not so clear to me, like what XRec is supposed to do.