Merge amplify branch into master

[rc-davis]

When we retire the last Netlify project, we should do the following (in order)

• Merge the isomer-build amplify branch into master
  • There will be conflicts with the netlify.toml file. All copies of this file should be deleted.
• Modify build.sh to download customHttp.yml from the master branch, rather than the amplify branch.
• Modify the amplify buildspec in isomer-tooling/site-creation-v2 to use the build.sh in the master branch, rather than the amplify branch (see amplify-publisher.ts build.sh).

This should also handle #24