Issue #1921224 by perohu, brantwynn: infinite loop removed when attempting to redirect users to the same environment

Issue #1917688 by brantwynn, Web Design Northern Ireland, PHP errors when mobile device switches back from override

#1917688 by brantwynn, Web Design Northern Ireland:  Handle exception if callback url is visited with no _SESSION variable set

Added .install file
Updated code/comments per http://ventral.org/