Add truncatable text field, use for some fields

Source + author are one such field, title is another.

Loads of the mingle card will be split out.

Change-Id: Ib2937cc55304118f82e5b2e87b822b2b2811ef2b
Mingle: https://wikimedia.mingle.thoughtworks.com/projects/multimedia/cards/243
Merge "Add truncatable text field, use for some fields"