CLI: various fixes

[jhnstn]

This includes a few fixes that were discovered during recent releases:

• Fixes release prepare all command so it can clone both Gutenberg and Gutenberg Mobile repos.
• Adds patch support to release integrate so that it opens the pr against the host release PR
• Adds ability to supply Gutenberg commit shas when creating a patch release
• Prompts to edit the Gutenberg change log on all releases.
• Prompts to create the release tag on Gutenberg.

This PR also includes updates to the documentation

Testing

Follow the Testing guide to set up the tool to use forked repos.

Scheduled releases

• Try running go main.go run release prepare all {version}
• Verify that there is a prompt to edit the CHANGELOG in gutenberg
• Verify that there is a prompt to tag the release and choose to not tag
• After completion verify that the tag was not created on Gutenberg

Patches

• Create a release branch on the host apps e.g. release/1.0
• Prepare a patch release using a few commits from your forked Gutenberg via the --shas flag
• Run the integration command with the host version used in the first step