Loader config file support

[cricketsloan]

Currently the CGP DSS data loader is configured using command-line options, and there is a substantial number of options that need to be set for each project/dataset to be loaded, and additional options that would be useful to support as well. Loading would be easier/faster and more reliable if all the options for loading a given project/dataset could be specified in a single configuration file, then the loader could simply be invoked with an option that specifies the config file name.

The configuration file format could be YAML or JSON.

The configuration file should support all of the settings currently available as command-line options.
In addition, there are more configuration options that are useful/important to support, which could be done as part of this story, or as a new story. These currently include:

• AWS Assume Role Duration

Done when:
All of the options currently supported by the CGP DSS data loader can be specified using a config file.

┆Issue is synchronized with this JIRA Story
┆Project Name: CGP-Data Loader
┆Issue Number: LOAD-65