Adding search to alt+f2

[Matt x]

    I would occasionally (not often) find useful an option to search for 
programs in the alt+f2 dialog, as you could in gnome2: start typing the 
name "thu" and get a list of matching programs (as long as results are 
shorter than a certain number?) below.  I think an option to disable 
this as well (off by default?) would be useful for those who want a 
smaller desktop resource wise.

-Matt