added a domain-account-level setting controlling whether or not the
scheduler is enabled. when it is turned on,
1. /calendar requests redirect to /calendar2 by default
2. both the new and old calendar pages include a link to the other
calendar (sets a user preference so that it redirects correctly in
the future)
Change-Id: I1817c7f8e9075282ab1988088f5c0ef8d63325f6
Reviewed-on: https://gerrit.instructure.com/7840
Tested-by: Hudson <hudson@instructure.com>
Reviewed-by: Zach Wily <zach@instructure.com>