Maintain 'Contributing to Rockstor' doc as canonical

[phillxnet]

Thanks to @StephenBrown2 for helping to highlight this issue. It is proposed that we move the following contributor related section of our rockon-registry README.md to our canonical contributor doc reference for the same: https://rockstor.com/docs/contribute/contribute_rockons.html

• https://github.com/rockstor/rockon-registry#one-time-setup-before-opening-pull-requests
• https://github.com/rockstor/rockon-registry#steps-to-contribute-a-rock-on-with-a-pull-request

[Hooverdan96]

Looking at this a bit more closely, this could be a refactoring approach:

In the Readme, keep this:

link back to the Rockstor docs and move (and merge or replace in the docs) these sections:

• Keep the header, ref to docs and move everything under How can I add ...
• Adding vs. Updating ...
• One Time setup ...
• Steps to Contribute...

Keep the What is the Structure where it is on the repo, but add a link in the documentation for it. I feel, since that's a fairly technical detail, and also describes a "living" structure under development (hopefully more soon :) ) it belongs there, but should definitely be referenced from the main Rockstor docs.

Furthermore, refactor this section in the Rockstor docs:
https://rockstor.com/docs/interface/overview.html#adding-rockons (since it references github sections a few times)

A possible plan would be to update the rockstor documentation first (with all above mentioned details), and then cleanse the Readme on github.

[phillxnet]

@Hooverdan96 This all sounds ideal to me. Thanks for progressing this issue more into the concrete realm.