* Implement export of HitMap plots.

* Implement Hitmap as separate struct and implement Plottable for it.

* Update crates

* Add OpticNode:hit_maps() and implement for various nodes.

* Add hit map to OpticalSurface

* fix:  Fix missing rays cache deletion in various optic nodes

* feat:  Implement ghost focus analysis for CylindricLens

* feat:  Add ghost focus support for wedge.

* Fix linter warnings

* Move ray cache to OpticalSurface. This version now simulates a double bounce forward focus.

* Add ray cache to OpticalSurface

* fix:  Fix bug while inverting an already inverted graph.

* Further work on ghost focus calculation

* First idea of a ghost focus analysis...

* Further work on AnalysisGhostFocus for Lens

* Update ghost_focus example and implement AnalysisGhostFocus for SpotDiagram & RayPropagationVisualizer.