Config Visualizer: Add support for multi-files configuration

• User impact:

  Low
• Similar Issues:

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My mule configuration is based on:

• a common file, where shared configuration elements are defined,
• node specific files, that inherit from the common one.

None of these files are usable stand-alone: Mule correctly loads and "merges" them at startup.

But the (very cool) Config Visualizer does not seem to support this, even if I use the -combinefiles option.