cleanup with operators/value tracker/current_state

- current_state now always computes its derived values
- it implements a copy function

testing/configs/Chang2011Fig2.toml

@@ -2,7 +2,7 @@ name = "/Users/benoitsierro/tests/test_sc/Chang2011Fig2"
 
 wavelength = 800e-9
 shape = "gaussian"
-energy = 2.5e-6
+energy = 2.5e-7
 width = 30e-15
 
 core_radius = 10e-6
@@ -11,9 +11,8 @@ gas_name = "argon"
 pressure = 3.2e5
 
 length = 0.1
-interpolation_range = [120e-9, 3000e-9]
 full_field = true
+photoionization = false
 dt = 0.04e-15
 t_num = 32768
 z_num = 128
-step_size = 10e-6