Reveal full text when user clicks on title or credit

Reveal the full title + author + source when the user clicks one
of these, and make some related changes:
* expand the above-the-fold part of the metadata panel so they fit
* make the stripe buttons smaller and hide their text
* scroll the panel up if necessary
* modify tooltip texts when there is more text to show

Change-Id: I304297bc5e7be7b16e2fc4bde66ac19641b00029
Mingle: https://wikimedia.mingle.thoughtworks.com/projects/multimedia/cards/396
Merge "Reveal full text when user clicks on title or credit"