ENT-824

LEARNER-5284

This results in a bunch of noise in the error logs, as well as weird
behavior when paginating through results for things like courses.

Add default status unpublished for newly created course runs, also update
existing course runs with null/empty status to unpublished.

LEARNER-5202

Co-authored-by: Uman Shahzad <uman@opencraft.com>

* Ignore all types of coverage files.

  I was getting things like `.coverage.$user`.

* Refactor existing serializers.

  Some serializers had their metadata all the way at the top
  of the file in separate variables, even though no other
  serializer were using those variables.

* Put things into proper places to make it easier to read
  and change, without having to jump up and down a 1000+
  line file.

* Add new serializers and use them in viewsets.

  These are the serializers for all 4 new endpoints,
  for courses, course runs, programs, and their aggregation.

* Add new mixin for detail endpoint.

  The mixin will add `/detail` to the end of whatever viewset
  that uses it.

* Call isort on the codebase.

* Refactor serializer test code.

  This will make it x10 easier to add tests for the
  serializers we introduced in this PR.

* Add test code for serializers.

* Refactor and add tests for viewsets.

Updated travis to use the i18n-tools validate
to validate translations in pullrequests.
LEARNER-2556

updated i18n-tool to latest version

-pull atleast 1% translated languages

-added push translations make target

-removed generate merge options

-removed i18n tools commands from extract translations

-removed existing translations

-extracted translations

-new translations

-compile messages

This reverts commit 2d188348.

Added salutation field in person model, also updated
refresh course metadata command and API to map this
new field.

LEARNER-4000

Increase the course run short description override db limit to count
for foreign characters.

LEARNER-4673

[LEARNER-4061]