Add —config to allow the user to specify the config (#2291)
* Add —config to allow the user to specify the config
* —config allows the user to tell cog which file
to look at
* This is useful when they have multiple configs
for different environments
* Fix lint
* Inject configFilename into migrator
* Change —config to be -f to conform to docker
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Signed-off-by: Will Sackfield <sackfield@replicate.com>
