Quantum noise sub-budgets

1. Adds quantum noise sub-budgets. This addresses 1/3 of #51 (closed). Quantum noise can now be broken up into

• AS port vacuum
• Arm loss
• SEC loss
• Filter cavity loss
• Injection loss
• Readout loss
• Quantum quadrature phase noise

2. Changes the quadrature phase noise calculation as described in the comments below. This should close #20 (closed).
3. Removes support for negative RMS phase fluctuations.
4. Removes call to shotrad4 in some cases since this function no longer exists.

The sub-budgets are only implemented for the Cosmic Explorer interferometers since these are the only ones that have any other sub-budgets. Adding sub-budgets to the other interferometers is easy. The CE2 quantum budget is shown below as an example.

gwinc/ifo/Aplus/__init__.py

@@ -2,6 +2,26 @@ from gwinc.ifo.noises import *
 from gwinc.ifo import PLOT_STYLE
 
 
+class QuantumVacuum(nb.Budget):
+    """Quantum Vacuum
+
+    """
+    style = dict(
+        label='Quantum Vacuum',
+        color='#ad03de',
+    )
+
+    noises = [
+        QuantumVacuumAS,
+        QuantumVacuumArm,
+        QuantumVacuumSEC,
+        QuantumVacuumFilterCavity,
+        QuantumVacuumInjection,
+        QuantumVacuumReadout,
+        QuantumVacuumQuadraturePhase,
+    ]
+
+
 class Aplus(nb.Budget):
 
     name = 'A+'