Added Temp/Perm Vehicle Spawn selection with images

Need to add this line in the description.ext, at the bottom of the file.
#include "admintools\dialog.hpp"

Selecting the menu the 1st time will take some time to load, but after
that it will pop out fast.
There are 3 buttons on the dialog window, "Temp", "Perm", "Close". Temp
spawn will make a temporary vehicle...etc
-Fix for dialog.hpp

Now it wont crash anymore...forgot to add the button definitions.
- Improved menu with Categories
- A fix for the 1st item in the list.
Merge pull request #9 from Sandbird/master

Added graphical vehicle spawn menu - all vehicles - categorized and available as "Temp" spawn or "Perm" - with a key.