Resolve "Add function to OpticNode for resetting a node"

Closes #329 (closed)

opossum/examples/ghost_focus.rs

+use opossum::{
+    analyzers::{AnalyzerType, GhostFocusConfig},
+    error::OpmResult,
+    joule, millimeter,
+    nodes::{collimated_line_ray_source, NodeGroup, SpotDiagram},
+    OpmDocument,
+};
+use std::path::Path;
+
+fn main() -> OpmResult<()> {
+    let mut scenery = NodeGroup::default();
+    let i_src = scenery.add_node(collimated_line_ray_source(
+        millimeter!(20.0),
+        joule!(1.0),
+        3,
+    )?)?;
+    let i_sd = scenery.add_node(SpotDiagram::default())?;
+    scenery.connect_nodes(i_src, "out1", i_sd, "in1", millimeter!(50.0))?;
+    let mut doc = OpmDocument::new(scenery);
+    let config = GhostFocusConfig::default();
+    doc.add_analyzer(AnalyzerType::GhostFocus(config));
+    doc.save_to_file(Path::new("./opossum/playground/ghost_focus.opm"))
+}