This is a set of improvements for the partitioning charts introduced with #493

• accessibility
• consider adding either more structure to the config (like linkLabel, which is already nested) - or alternatively, rely on a flatter structure for composable configurability
• review types for improvement opportunities
• outside link label improvements: value display; length limitation;
• outside link label improvements: avoidance of truncation due to chart port size
• feed styling from Theme, for what's possible and suitable refactor(partition): remove config in favor on spec and theme controls #1402
• break up long functions eg. shapeViewModel
• add unit tests
• check results in the legacy browser
• pointer events
• further work on Pie/sunburst chart - discussion about small slices #381 Provide dimension lookup in a star/snowflake schema style #464 Handling colors #492