Remove duplicated data from legacy events

When event-tracking was fully integrated into the platform, some data was replicated in the context in the middleware and then later extracted and moved the old location by event-tracking. The legacy code path was not updated to remove this transient shim data from the context resulting in duplication of the information. This patch ensures that the transient information is removed from the context before emitting the event.

Fixes: AN-2369
Add Eng (GB) and Albanian lang codes
Update translations (autogenerated message)
Annotation Tool: Flagging plugin should now allow instructors to remove flags from annotations

Annotation Tools: Added lots of comments, fixed spacing, fixed slice issue

Annotation Tools: i18n fixed for this tool

 - fixed Translator to Translators

Annotation Tools: Removed unnecessary class and worked with element object
Instructors can view previously sent email content

Previously on the send email page of the instructor dashboard, instructors could only view
task information about emails they've sent for their course in the past.
In addition to this, I've now added the ability to see the content of all previously sent emails.

A "Sent Email History" button has been added to the page. When clicked, a table displaying the
subject line, number of emails sent, and date/time of submission for each previously sent email
is created. An instructor can then click on any subject line to see the content of that email,
displayed in a modal window that appears on the page.

The window is also equipped with a "copy email to editor" button, which copies the emails contents
to the tinyMCE editor, so that an instructor can easily resend an email that they've sent
in the past.
Notification UI