Add metrology element (change of base, computation of error)

Lot's of new things:
- try to use less .mat files
- computation of setpoint and error in the cartesian frame fixed to the granite
- change of base to have the errors w.r.t. the NASS base
- add script to plot setpoint, position and error

Analysis/ground_motion_ol_cl.m

@@ -123,7 +123,7 @@ exportFig('gm_control_psd_y', 'normal-normal')
 
 %% Compare OL and CL - PSD
 load('./mat/G_xg_to_d.mat', 'G_xg_to_d');
-load('./mat/weight_Wxg.mat', 'Wxg');
+load('./mat/perturbations.mat', 'Wxg');
 load('./mat/T_S.mat', 'S', 'T');
 
 freqs = logspace(-1, 3, 1000);