Make it obvious that the permission text is cut off; add expand link

Fades out the bottom of the text and adds a link to replace it
with the full HTML version. Due to the way it is positioned,
the fade + link will be invisible if the text is less then 3 lines.
The implementation is not very polished; since this will be
replaced by some JS-based ellipsis thing, I didn't want to spend
too much time on it.

Change-Id: Ib30e40fe845b85bfcf9557970efb886d28b3e5c7
Mingle: https://wikimedia.mingle.thoughtworks.com/projects/multimedia/cards/118
Merge "Make it obvious that the permission text is cut off; add expand link"