Big code and command cleanup

[dafeder]

Pretty major reorganization and consolidation. This should probably be followed by a new major release.

• Remove "get" commands
• "init" results in a ready-to-install composer.php file, including DKAN dependency
• Make is only responsible for installing dependencies
• Docker/proxy commands greatly consolidated
• bash script much more readable
• All classes have been cleaned up and simplified as much as possible
• Frontend commands are reorganized:
  • frontend:get is optional, takes --url and --ref arguments but defaults to a new "extra" config object in the DKAN composer.json
  • frontend:install will run frontend:get if no frontend is present, or otherwise try to run npm:install on whatever is in /src/frontend
• Tests are now run using shuinit, better simulating real developer usage
• Site-specific tests will now live in a project's src/command/SiteCommands.php file rather than in DKAN Tools

Also includes commits from:

252 (Peg docker images to specific tags)

229 (Switch to data-catalog-react frontend repo)

255 (Refactor bash script for readability/maintainability)

245 (Docs build command)

QA Steps

Mostly just try to do your normal work, but here's a basic QA script

dktl init
dktl make
dktl install
dktl install:sample
dktl frontend:install
dktl frontend:build
dktl url
dktl drush uli

Other things to try

dktl init --drupal=[another drupal version]
dktl init --dkan=[another dkan version]
dktl frontend:get --ref=[branch or tag of data-catalog-react]

dktl init
dktl demo # These two will get you a working demo site with sample content