Text changes for Email Sent by addition
A better check for the existence of matlabinput element.
Outline for release notes
Removed grading and drag'n'drop
release notes tweaks
add tests for drag and drop unit into collapsed subsection on course outline page
update/cleanup code + move verify_ordering and drag method to studio utils
login, registration, and dashboard page changes for third-party auth
Facebook auth support.
doc-byte-sized-tasks: Add link to the byte-sized tasks in CONTRIBUTING

Thanks to @adampalay, we now have a list of byte-sized tasks, which are
useful for new contributors who want a gentle introduction to the
platform. This PR adds a link to the tasks tagged as byte-sized in the
public tracker.
Merge pull request #4972 from open-craft/doc-byte-sized-tasks

doc-byte-sized-tasks: Add link to the byte-sized tasks in CONTRIBUTING
Implemented Validation for Course Advanced Setting

This commit adds validation for course advanced settings. Currently when course
administrators make invalid changes in the Settings/Advanced Settings tab,
they're not notified through a new modal window of the list of invalid settings
changes.

* Extending CourseMetadata
    - Previously, we only had update_from_json method in CourseMetadata.py,
      and it was only validating one field every POST request.
    - Now we have validate_and_update_from_json method that encapsulates the
      functionality of update_from_json into a validation call
    - To avoid discrepancy of validation standards between modules, validation
      uses the from_json method implemented to each field in xblock.

* Different Response in advanced settings ajax requests
    - After receiving a POST ajax request, course.py calls
      validate_and_update_from_json, and sends a json object of either:
        1) valid course metadata model
        2) error objects

* Error Messages shown in validation-error-modal
    - error objects passed through ajax are shown in a separate modal.
Updating the Login button to have the same hover style as Drupal
djpyfs is installed app not middleware
release notes initial draft
Merge pull request #4974 from edx/bug/djpyfs

Bug/djpyfs
Merge pull request #4935 from edx/ahodges/doc/DOC914

Removed grading and drag'n'drop
Fixup of Bug/djpyfs
release nets include Sylvia's comments
email history sender images