parameterize configuration files

This issue aims to resolve the following:

The config file is a dump of all of the required information that is needed by fmbench to benchmark models, such as dataset details, experiment information, but in some cases, most of the parameters are placeholders and only a few parameters need to be changed. For this, we need to come up with a standard way to have a base config file and the most important parameters that a user would want to change parameterized as a part of command line arguments.