Follow up on linktrail / template interaction

 * f72c9653e16db9bbe959ceca1e63760abca62a1c assumed that the link would
   be the first encapsulation wrapper node which broke, for example,
   ruwiki:Красностовский,_Алексей_Иванович

 * Here we make sure that for prefixes, we are indeed the first one. For
   trails we check that there are no about siblings and if not, find the
   first wrapper. Otherwise, we can assume that encapsulation will
   handle interaction.

 * Test case from that page would be,
     echo "Родился {{СС|28|марта|1880 год|15}}а в" | node parse --prefix
     ruwiki --wt2wt

 * Adds two new passing tests. One selse failure, but seems like it has
   to do more with a trailing newline.

Bug: 60752
Change-Id: Iaa1a268fbf2e6fdbb26beabf6d2601cb44a44469