Quantum Noise h_SQL should be defined in terms of sustf.tst_suscept

Now that the radiation pressure is properly calculated from the testmass susceptibility, the SQL factor used should not be the analytical value calculated under the free mass assumption.

line 300 from quantum.py should go from h_SQL = sqrt(8 * hbar / (m * (Omega * L)**2)) # SQL Strain

to

h_SQL = sqrt(8 * hbar / L**2 * abs(sustf.tst_suscept)) # SQL Strain

It's a pretty small adjustment to the noise, only about .2% around 10Hz in the aplus model. I'd like this since A) it is correct and B) quantum code I'm working on needs correct comparisons.