Updated the multi-stage-builds Docker concept page to include a
prerequisite for Java. Also updated the link and screenshot for the
Spring Initializer to the latest version.
The Dockerfile and Dockerfile.multi are created in later steps. The `springbootdocker` directory appears to be named `spring_boot_docker` in current download.
The build guide that I once wrote now duplicates a lot of content with
the concept guide launched a few months back. It doesn't make sense to
cover the same topics multiple times, so I'm removing the older build
guide and incorporating some of the topics into the build manual
instead.
Signed-off-by: David Karlsson <35727626+dvdksn@users.noreply.github.com>
