rolap 2.4.0

• Functions to query a star database: star_query(), select_fact(), select_dimension(), filter_dimension() and run_query().
• Functions to deploy a star database in one or more relational databases: deploy(), cancel_deployment(), get_deployment_names(), load_star_database().
• New functions: get_star_database(), as_rdb(), draw_tables().
• Vignette about star database deployment process.
• Vignette about star database export features.
• Vignette about multidimensional queries.
• Include new items in the README file.
• US census flat table dataset.
• Fix snake_case() register refresh operation for constellation case.
• Fix constellation() refresh structure integration.