Multiple data support for a single entity

[eblondel]

The geoflow data model should evolve to support multiple geoflow_data objects for a single geoflow_entity.

As first objective, this will not be implemented through the basic tabular metadata handlers, and a new handler will be designed to deal with a Data directory, from which geoflow_data objects will be built. The geoflow data model should be backward compatible to make sure ongoing workflows in which entity$data is a geoflow_data keep working as it is.

The handler based on a data directory should be a convenience for doing batch publication of ISO/OGC data products, where a single metadata may refer to several data objects, ie several layers.

• Implement nested/child geoflow_data objects in case of a multiple data directory for target functions including entity$copyDataToJobDir, entity enrichment functions, and actions that manipulate geoflow_data objects in particular the geosapi one targeting the enabling of OGC data services
• Implement backward compatibilie change for use of geoflow_data single or multiple objects
• Merge 'enrichWithFeatures' / enrichWithCoverages' into single 'enrichWithData' Merge 'enrichWithFeatures' / enrichWithCoverages' into single 'enrichWithData' #264 and implementation into executeWorkflowJob and debugWorkflow
• Enable data enrichment strategies ('first', 'union') Enable data enrichment strategies ('first', 'union') for spatial bounding box #265