Deprecate and Remove LTI 1.1

[jrjohnson]

We currently support both v1.1 and v1.3 of the LTI spec, we should start to move everyone away from 1.1. There is no real security improvement for us in the new standard because we're not exchanging data and if someone used the possible CSRF attack vector in the old standard all they would do is shod their Ilios calendar to the person who was misled.

However supporting both is more to manage, so let's move to the new exclusively.