Add Rules Parsing for Files

Add the basic framework for rules parsing. The input is a json file
with two sections: one for files and another for folders. With this
change only files are checked against a 'match' attribute on each
file rule.
Add Comments to load_rules and process

Add some method comments to these methods.
Add Rule Validation

Add basic rule validation to ensure at least 'file' or 'folder' exists.
The process method assumes both exist so if one is missing, it is
added to the rule list. If both are missing an exception is thrown.