Handle <th> elements in {{Information}} template

So far we assumed all cells in the left column of the info template
are <td>s, which is not the case (even though COM:MRD does prescribe
it).

Change-Id: I78071b119eaa808de4a46addf8305136f7639c11
Mingle: https://wikimedia.mingle.thoughtworks.com/projects/multimedia/cards/249
(cherry picked from commit 179a830b958a10c3048a10fd9dacc52d617075c2)