Allow overriding individual config settings from outside docker container. (#1100)
Allow overriding individual config settings from outside docker container. (#1100)

This allows patching specific config settings from the environment so the settings can be tweaked without modifying the docker container.
parthea/datalab,craigcitro/datalab,googledatalab/datalab,parthea/datalab,googledatalab/datalab,craigcitro/datalab,yebrahim/datalab,craigcitro/datalab,parthea/datalab,parthea/datalab,googledatalab/datalab,craigcitro/datalab,yebrahim/datalab,parthea/datalab,googledatalab/datalab,yebrahim/datalab,yebrahim/datalab,parthea/datalab,googledatalab/datalab,googledatalab/datalab,craigcitro/datalab,yebrahim/datalab