Miscellaneous fixes to strings found during i18n work.

cms/templates/registration/reg_complete.html

lms/djangoapps/shoppingcart/processors/CyberSource.py

lms/static/admin/js/calendar.js

lms/static/admin/js/dateparse.js

lms/templates/static_templates/server-overloaded.html

lms/templates/verify_student/_reverification_support.html

lms/templates/verify_student/_verification_support.html

lms/templates/verify_student/show_requirements.html