Integrate YAML project feature models with standards mappings

[SvenPeldszus]

This integrates YAML-based project feature models into org.gravity.typegraph.spl on top of the existing FeatureIDE-based variability infrastructure.

Key changes:

• add .yaml/.yml loading through FeatureModelLoader while preserving existing FeatureIDE formats;
• parse nested project features into FeatureIDE IFeatureModel instances;
• support canonical security-feature names and direct standard-control mappings in YAML;
• add a curated feature-to-control mapping catalog with aliases, provenance, relation and confidence;
• resolve mappings to actual EMF Control EObjects from dynamically loaded standards models;
• add examples, documentation and tests;
• bundle SnakeYAML in the Eclipse plug-in using the repository's existing dependency-copy pattern.

The implementation deliberately does not change Spl.ecore: the existing SPL metamodel remains focused on TPresenceCondition, while project features continue to use FeatureIDE's IFeatureModel, as VariabilityAwareProgramModel already does.

Validation note: the new Java source was syntax-checked locally against API stubs, but a full Tycho build could not be run in the execution environment because the repository could not be cloned there. This PR is therefore opened as a draft pending CI/full workspace validation.