Tweaks to documentation

• Update spacing of images in README
• Make git commands more usable in README
• Reformat CHANGELOG.md

Changes for open source release

• Remove unneeded warnings in install.sh [#1482]
• Add instructions on creating content to the README [#1487]
• Add information on the JSON files that are produced to the README [#1488]
• Add Overview to README [#1507]
• Add base content and configurations to Drupal in install.sh [#1509, #1501, #1511, #1512]
• Use a $DIR_ROOT variable for where install.sh should do its work [#1514]
• Use same colors for output that the client install.sh uses [#1515]
• Add example API URLs to README [#1516]
• Add comments to code in README [#1517]
• Correct install.sh error Could not find the permission: access administration menu [#1518]
• Add composer.json to repo [#1519]
• Add uninstall.sh script to repo [#1520]
• Add instructions to add artworks and tie them to themes to README [#1521]
• Add CHANGELOG.md [#1506]