Flow around sphere

This MR deletes the FlowAroundSphereCodeGen from the benchmark cases. Instead, a new FlowAroundSphere application is provided that is integrated into showcases. The focus of this application is not benchmarking anymore but on physical analysis of the flow around a spherical object. In particular, the new application is capable of reproducing the drag crisis as reported in the literature.

Dependes on !685 (merged) Closes !633 (closed)