Add a way to render the state

Note that this has exposed some scaling error that needs to be fixed.

src/render.rs

@@ -0,0 +1,17 @@
+use crate::SimState;
+
+pub struct NumericTermRenderer;
+
+impl NumericTermRenderer {
+    pub fn render(&self, state: &SimState) {
+        print!("E:   ");
+        for cell in state.cells() {
+            print!("{:>8.1e} ", cell.ez());
+        }
+        print!("\nB:   ");
+        for cell in state.cells() {
+            print!("{:>8.1e} ", cell.by());
+        }
+        print!("\n");
+    }
+}