Fix incorrectly scoped selector.

If the first date the user selects is invalid it is not set on the
model. This is because jQuery datepicker's getDate returns the
current date when an invalid value is put in the field and the
model's initial value is also the current date. So always update
the date.

TNL-4115. Previously, course updates (which are intended to be posted with
dates, for sorting in the LMS) could be authored in studio with a valid
date, nothing, or a random string as the "date" for the update. As there
is no validation for this in studio, everything succeeded with no warning.

However, the LMS has problems parsing some of these values, and barfs when
loaded by learners.

The fix does two big things:
- gracefully handles invalid dates in LMS. These updates are now treated as
having a date of today, for sorting purposes.
- turns on validation in studio. Now, it is not only impossible to enter
invalid dates in studio, but notifications will draw the course author's
eye if any invalid updates were previously saved.

Test additions for this commit:

Adds:
- unit test for LMS parsing
- Jasmine test to confirm invalid dates cannot be set by the user
    -also adds event to setAndValidate instead of using a global object
- fix for lettuce test
    -It is no longer valid to enter the string "January 1, 2013" as this test
    had been doing. Keyed-in entries must use MM/DD/YY format.

When a course is updated, track whether or not a push notification is
sent.

It's a problem for accessibility

STUD-1404

Add baseview(extended from backbone view), which can further extended by other views + Add fucntion to modify iframe and embed tags + add related tests
STUD-823

Move overview-specific functions into overview.js.

Fixes bug STUD-822.