rundialog: update with new design

Introducing new design for rundialog. Now it has a Grid
which displays all the results come out from the search.
It is also possible search through the Application's Keywords,
Description, Name, and so on.

Design based on GRunner: http://youtu.be/iQX6DFHRqFk
Refers #104
launch first item on pressing return
rundialog: use a Gtk.reveal as effect for the results
rundialog: add headerbar with preferences and close buttons
rundialog: fix default width
rundialog: add suggested-action class on the fist item
vapi: fix gdesktopappinfo search return value
rundialog: add info labels which show app's description and exec commmand
Merge pull request #123 from LeoIannacone/master

New design for run dialog