CMS-4016 Schemas in modules - Make SchemaKey composed of modulekey+schema_name
CMS-4015 Schemas in modules - Create base API classes to support providing schemas from any OSGi bundle
CMS-4037 Schemas in modules - Implement SchemaProvider classes to replace schema initializers
CMS-4037 Schemas in modules - Implement SchemaProvider classes to replace schema initializers.
Grouped the Core*Provider classes in a single class CoreSchemasProvider.
CMS-4038 Schemas in modules - Update schemas in SchemaRegistry when a module is stopped/started
CMS-4038 Schemas in modules - Update schemas in SchemaRegistry when a module is stopped/started.
Fixed references to specific schema names (site, image).
CMS-4038 Schemas in modules - Update schemas in SchemaRegistry when a module is stopped/started.
Merging from master.