Initial Koa release notes (openedx#1906)

* Initial Koa release notes

Copied from
https://docs.google.com/document/d/14DZIIIBIO_pOjPX9jjIqwG2pjUM2yr26S_aLmvA06qU/edit#

* A better link for the Koa installation

We want to have a new installation page for every release going forward
so calling it "Koa" is appropriate.

* Add depeendency upgrades

* Add paragraph about XBlock conversion

* Add deprecations

* ORA2 updates for Koa

* Fix links and typos

(cherry picked from commit bf78d46)

Initial Koa release notes (openedx#1906)

* Initial Koa release notes

Copied from
https://docs.google.com/document/d/14DZIIIBIO_pOjPX9jjIqwG2pjUM2yr26S_aLmvA06qU/edit#

* A better link for the Koa installation

We want to have a new installation page for every release going forward
so calling it "Koa" is appropriate.

* Add depeendency upgrades

* Add paragraph about XBlock conversion

* Add deprecations

* ORA2 updates for Koa

* Fix links and typos

(cherry picked from commit bf78d46)

Update edx-platform code refs to use correct import paths (openedx#1892)

Code within edx-platform djangoapps should be referenced
via its full path. For example,
    `track.tests`
should now be referenced as:
    `common.djangoapps.track.tests`.

The old import paths are deprecated.

(cherry picked from commit 2ac3bf6)

Release details are now on readthedocs

(cherry picked from commit b427e44)

Release details are now on readthedocs

(cherry picked from commit b427e44)

Release details are now on readthedocs

(cherry picked from commit b427e44)

The Open course book should have the same getting started target as t…

…he partners book DOC-4021

(cherry picked from commit 7c5422e)

Public Course Content

(cherry picked from commit 603a8db)

Public Course Content

(cherry picked from commit 603a8db)

Format fix