cherry-pick commits to the release branch

931e40a (Luca Heltai, 20 hours ago)
   Now also cached variables have CPACK prefix.

57460cb (Timo Heister, 16 hours ago)
   fixup files

cf49cd7 (Timo Heister, 16 hours ago)
   more fixup

c9af9b2 (Timo Heister, 16 hours ago)
   format everything

d3af12b (Timo Heister, 17 hours ago)
   fix warpcomments.py

d9ea8d2 (Timo Heister, 17 hours ago)
   fix up more files

482cefe (Timo Heister, 17 hours ago)
   fix more files

54100f5 (Timo Heister, 17 hours ago)
   force @ref in separate line

8aff68a (Timo Heister, 17 hours ago)
   put @ref in separate line

1970f42 (Timo Heister, 2 days ago)
   remove stray comment

9043ad1 (Timo Heister, 2 days ago)
   update wrapcomments.py

   now handle @image tags correctly

c613a01 (Timo Heister, 2 days ago)
   fix doxygen formatting

   reformat a couple of places in the doxygen comments manually (broken
   @image lines etc.). This is mostly to make wrapcomments.py happy.

cf40de3 (Timo Heister, 2 days ago)
   improve SolutionTransfer exception

   parallel::distributed::SolutionTransfer only works with
   parallel::distributed::Triangulation. This is now checked in the
   constructor.

f441f7b (Timo Heister, 2 days ago)
   add .gitattributes

   we ignore the testsuite and some other files when creating a tarball with
   git archive. This is also used by github for 'releases'.