Docker fix healthcheck; allow modules; cleanup; set uid The docker healthcheck was hardcoded to check the /issues/ tracker. Replace healthcheck with one that looks for the tracker names on the roundup-server command line and checks the first one. During build, additional modules can be specified using --build-arg="pip_mod=requests setproctitle". This lets the user add modules unique to the tracker without having to 'docker commit' a new image from a running container. Use --build-arg="roundup_uid=2000" to change the uid roundup runs as. The default is 1000. This is done at build time, not run time. Remove the sphinx package. All the dependent packages were removed before, but sphinx wasn't. This led to spurious warnings fom the pip dependency resolver. Update docs with changes.

Babel
Jinja2
MarkupSafe
Pygments
alabaster
certifi
charset-normalizer
docutils
idna
imagesize
packaging
pyparsing
requests
six
snowballstemmer
sphinxcontrib-serializinghtml
sphinxcontrib-websupport
urllib3