I hate this quick and dirty hack but it makes no sense to port to
master. This fixes a bug whereby we'd build with the master Web branch
on releases due to never checking out the right branch. This is already
obsoleted in the master branch since #1925 already replaces this entire
process for Debuntu builds, and others should be fixed with a more
robust solution. That said, for the 10.4.z release chain, this
ultra-quick solution fixes the problem without changing much.
1. Update README.md to remove some old info
2. Remove common.build.sh from all the build scripts
3. Remove common.build.sh script
4. Remove the docker folder as this isn't used at all
