Implementation of the IStorageProvider interface using Eclipse file resources as storage mechanism for models.

This storage provider searches all projects in the Eclipse workspace for model files. Only files in the project's root folder are considered. For each such files the set of registered eclipseResourceStorageLocationProvider extensions is asked whether the respective file should be considered a model file. This extension mechanism is used to allow independent tools (running in the same Eclipse instance or two RCPs running independently) to use different file extensions for their models, e.g., tool A uses file pattern "*.toolA", while tool B uses the file pattern "*.toolB". The file extension is usually a hint on the meta-model class of the contained root model element.