username and email request for lti module

Necessary for MIT course starting early October. Please merge as soon as possible to facilitate feature testing.

added username and email functionality, so that username and email can be passed to the lti third party app
Sorry if it is stupid question: what if student does not want his email to be passed to 3rd party app.? How he can say that? How can request policy of data storage from 3rd party app? He will drop the course or skip the unit if he insist?