Cleanup docker before 2.3.0b1 release scripts/Docker/Dockerfile Document/implement pip_sdist source mode for testing the source distribution. Change from multiple if's to case statement. Disable verbose tracing of shells script. Use --build-arg="VERBOSE=1" to enable set -xv. scripts/Docker/roundup_start Report error if demo mode is used with 2.2.0. This catches the easiest case where build is done using pypi before 2.3.0 final is released. Indent demo mode PORT_8080 doc block so it's not lost in a wall of text. doc/installation.txt Document all source --build-args including how to build from pypi using a version specifier. Break out other uses of --build-arg into code blocks. Reference docker compose section rather than referencing docker-compose.yml. Clarify docker hub tagging for devel releases. Minor formatting fixes.

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