Displaying additional data in Select2 combobox and tokens

Now combobox and tokens input type in Semantic Forms can have
additional data like thumbnail images and description
displayed along with the autocomplete values. This is done
with the help of external data extension that is used to fetch
data from any url.

Change-Id: I9b65c8b04e1d2a22ef6af9203c62201207416a6c
Merge "Displaying additional data in Select2 combobox and tokens"