Add plugin framework for external MATLAB-based tools

[George-R-Heath]

Implement a basic plugin architecture to allow integration of external MATLAB apps (e.g., Trace_y, fibreProps). Each plugin will reside in the plugins/ directory and will include a standard entry point script.

Tasks:

• Define folder structure for plugins (/plugins/PluginName/)
• Add launch_plugin(pluginName, optionalArgs) function
• Add error handling and logging if plugin not found
• Document how to create and register a new plugin