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* User explicitly creates balsam DB directory with "balsam init"
* User launches DB server with "balsam dbserver"
* user_settings is vastly simplified...moved all configuration logic
into django_config module
* Database is auto-configured on django startup; will connect to DB
server automatically if client

cli_commands: fixed small user error message bug
model saving: more robust retry: wait and check if save succeeded in
spite of the exception

This reverts commit 74ce64c5

(e.g. balsam ls --state JOB_FINISHED)

Fixed bug (inconsistent variable naming) which caused ranks_per_node
not to be assigned correctly by "balsam qsub" command line

DAG functional tests; bugfixes in launcher and runners. mpi_ensemble reads envs directly from database