Optionally merge in a girder configuration file.
Optionally merge in a girder configuration file.

The girder.local.cfg file in the histomicstk container can be modified
by the provisioning process to merge the current file with a file
specified by a command line parameter.  For instance, `deploy_docker.py
provision --cfg=sample.cfg` will add the local file `sample.cfg` into
the existing configuration.

DigitalSlideArchive/HistomicsTK,DigitalSlideArchive/HistomicsTK