(issue1754) Proper subtitle handling for Radius This deduplicates the subtitle and zoom / radius calculation code by moving it out of the processors. Doing this fixes cases where the subtitle would be removed when a the according filtered facet was removed although it should still have shown the Range for example. Range is now also added as a subtitle for the difference diagrams. This adds some tasty hack (with cheese) to determine wether or not the user has set the subtitle. See the comment in getChartSubtitlePure in LongitudinalSectionGenerator2 for details.

- Validation of the input values of an incoming feed() call