Docs: Octavia developer quick-start guide

[Stephen Balukoff]

As with neutron-lbaas, in order to increase participation and adoption of the project as Octavia gains traction, we should do more to help new developers and vendors looking to add drivers to have an easier time getting to know our ways of doing things. To this end, I propose we create a developer quick-start guide. This should cover things like:

* Links to how to contribute
* Links to wiki resources (meeting schedule, minutes, agenda, IRC channel)
* How to devstack Octavia
* Update project roadmap
* Links to release notes
* Considerations if you are a vendor looking to write an Octavia driver (eg. "if you can't run as a virtualized appliance, you're going to have a bad time.")

(See https://etherpad.openstack.org/p/lbaas-octavia-docs-needed )

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/410419

[OpenStack Infra (hudson-openstack)]

Change abandoned by Adam Harwell (<email address hidden>) on branch: master
Review: https://review.opendev.org/410419
Reason: This review is > 4 weeks without comment, and failed Jenkins the last time it was checked. We are abandoning this for now. Feel free to reactivate the review by pressing the restore button and leaving a 'recheck' comment to get fresh test results.

[Gregory Thiemonge (gthiemonge)]

Abandoned after re-enabling the Octavia launchpad.