[text-combo-box] allow user to change index and title properties
[text-combo-box] allow user to change index and title properties

Also print the value of these properties when they change.

clutter-project/mx,pwithnall/mx,clutter-project/mx,clutter-project/mx,jonnylamb/mx,pwithnall/mx,jonnylamb/mx,jonnylamb/mx,pwithnall/mx,clutter-project/mx,pwithnall/mx,jonnylamb/mx