BLD-543: Fix bug with reordering in Studio.
Fix tests.
Address comments.
BLD-413: Add rounding of coordinates.
Address comments.
Fix comment.
Add default email settings

These are the django default settings.
Add email configuration to cms/envs/aws.py

This allows emails to be sent by Studio.
Minor changes by Valera.
Turn off AUTH_USE_MIT_CERTIFICATES
Fix missing _ import.

Fallout from #1792.
Fix another unbound underscore
Merge pull request #1891 from edx/anton/fix-lti-dnd

LTI: fix reordering bug in Studio
Merge pull request #1917 from edx/anton/fix-imageresponse-in-ie

Fix image mapping in IE
Merge pull request #1924 from edx/db/turn-off-mit-auth

Turn off AUTH_USE_MIT_CERTIFICATES
fix external_auth @ssl_login_shortcut decorator to properly use retfun
add missing retfun
remove @cache_if_anonymous
Added full test coverage for ssl login decorator
I also removed conflicting implementation of SSL_AUTH_IMMEDIATE_SIGNUP
and rebased on the current master.
Added comment as requested