SAK-25286

Add method to BasicLTIUtil to help in mapping URLs when behind a proxy server

BasicLTIUtil.getRealPath(request, "https://www.mooc.edu"); 
BasicLTIUtil.getRealPath("http://serv01.mooc.edu/path/blah/", "https://www.mooc.edu"); 



git-svn-id: https://source.sakaiproject.org/svn/basiclti/trunk@130406 66ffb92e-73f9-0310-93c1-f5514f145a0a