Incorrect warning messages for nested JSON configuration files

[tpr1]

Federate configuration files that contain multiple closing braces (example) result in multiple warning messages about missing parameters.

The config parser checks for End of File using a closing brace rather than the actual end of file:
https://github.com/SimIntToolkit/cpswt-core/blob/develop/cpswt-core/config/src/main/java/org/cpswt/config/ConfigParser.java#L54-L57

This means that all parameters after the first closing brace in the file are not inserted into fieldsSet and trigger this warning message. The config parser should be modified to read the entire configuration file, rather than up to the first closing brace, when parsing the fields.