Bunch 'o Things

-- Fixed a lot of broken links for js files in Problem.pm UserList2.pm ProblemGrader.pm etc...
-- Made it so that backticks work with formatting essay questions.  (Doesn't complain about variable out of context)
-- Added tabber to Achievement Editor in all themes
-- In theme math4 javascript is used to replace tabber by bootstrap tabs.  Unfortunatelly this still requiers tabber to be there and running, even though its not directly used)
-- I mostly disabled facebook integration.  It can still be used but because of the way facebook works each school that wants to use it has to create their own facebook app.
-- Fixed a bug where deleting a student didn't delete all their achievement information