Fix bug DNN-3371: when index journal module first time, we aslo index journal items which is not post from jounal module and also the post module doesn't implement feature of search.
Fix bug DNN-4209: Obsolete UserProfile.PhotoURLFile, use FileManager API to load user photo and create thumbnails. also correct some invalid xml comment.
Fix bug DNN-4209: create thumbnails with correct name.
Fix bug DNN-4427: hide the join group button when the group is not public.
Fix bug DNN-3599: add an option "Unlimited" in message length drop down, and DO NOT limit the length when select it.
Revert "Fix bug DNN-3371: when index journal module first time, we aslo index journal items which is not post from jounal module and also the post module doesn't implement feature of search."

This reverts commit 1543d6c3c9c26608864c6ebc2b7fd007d441f81b.