* [767]: Update the run-sims-with-all-dbs script to exit with a non-zero code if one or more of the tests did.

* Add the CONTRIBUTING.md doc to the docs updated by the update-tocs target.

* [767]: Update CONTRIBUTING.md with more accurate branch and release info

* Remove some Cosmos-Specific pieces.
* Replace some references to Cosmos-SDK.
* Update some of the PR stuff to reflect the current process.
* Refactored the "Branching Model and Release" section by splitting it
  in two and more accurately describing our branching and release
  process.
* Updated the TOC using our auto-TOC script.

* Undo the run-sims-with-all-dbs change and do that in a separate PR.

* Some tweaks after reading through it again.

* [1143]: Update the Testing section in CONTRIBUTING.md.