Add feature flag for disabling course start dates

Conflicts:
	common/djangoapps/student/views.py
	lms/djangoapps/courseware/courses.py

Dormsbee/hack fix pwd reset

Django hardcodes the subject line for password reset emails. You're supposed
to be able to override it with a properly named template, but that didn't
make it into 1.3.1 (which is what we're deploying on now). We're not using
the Sites framework at this time, so this was the "fix".

Actually, the bg play YT bug was there because of the lack of a class on the section. Re-removing the YouTube title.

Reverting the YouTube title hiding commit because it brings back the 'video playing in the background when you hit back' bug

Bad hardcoded hack fix to password reset.

We used to use Django templates and the Sites framework. At some point we
stopped, but this was leftover. The site_name no longer gets set properly.
It's probably a config issue, but not one I want to deal with right before
release, so I'm hardcoding it to link to the prod edx.org site until we
 can sort what's what in the morning.

Release fixes

Dormsbee/help

Fixed bugs caused by modal cloning. Now, only video modals are cloned.

Dormsbee/jobs desc

Fix for appending course enroll to login/register form

Added styles for help page

IE fixes!!!!!!!!!!!!!!!