Update requirements installation commands for course discovery.

Clarify some docker conventions

See edx/course-discovery@7482d0e4.

discovery play fixes

Add script & playbook for reporting on package upgrades

Add some docs, fix some bugs

OPS-1240 Datadog role erroring and causing builds to be marked failed

Add another MIME type for Javascript files.

Enroll test users into testcourses as part of provisioning.

We need test users automatically enrolled into these courses so we
can automate various tests (most immediately, fully-deployed sandboxes
that we run browser testing against.)

See: TE-1128

Erroneous removal in a1509d2e

SEC-79: Install nginx from their ppa

E0d/change name coursediscover

Merge Dogwood changes (so far) into master.

Do the fast checks first and then the slow docker tasks.

Print only the 10 slowest tasks instead of all of them.

add jwt auth settings for edxapp role

Move to using a more recent build for the default devstack.

Max/idempotent mongo 3 0

MA-1955: Add OAuth expiration config.

The dogwood devstack was not compatible with some changes made after dogwood was cut.

DEVOPS-3275 Add theme selector to Jenkins ansible-provision job

Add verbose option to aid debugging failed builds

Previously on this branch, it would attempt to create a superuser and
initialize the replica set after the local host exemption had passed
(once a mongod is started with a keyfile and the replicationSetName
 config file option or --replSet command line argument, you can't create
 users using the localhost exemption anymore ).

This necesarily complicates the logic and requires us to track if we're
initializing a replica set or not (with facts) and to template out
/etc/mongod.conf twice in the initialization case.

Further modifications to the replica set can be run against all the
members and will install mongo on new machines while updating the
replica set on the old machines.  With a further commit on this branch,
we can avoid needlessly restarting mongo on all machines in the cluster.

When we run this on an existing cluster, this stops and starts mongo for
all machines it is run against.  We can't rely on the notify: since that
happens at the end of the play and during initial cluster setup, we need
to restart and pick up the changed config.

Try to stick sensible tags on things

Ensure mongo restarts on the cluster key file change

Add a few playbook notes about common operations