Add 3d convergence study results

tests/3d_r13/referrors/r13_kn0.005_shell/errors-1.csv

+h,theta_L_2,theta_l_inf,theta_H_1,s_L_2,s_l_inf,s_H_1,sx_L_2,sx_l_inf,sx_H_1,sy_L_2,sy_l_inf,sy_H_1,sz_L_2,sz_l_inf,sz_H_1,p_L_2,p_l_inf,p_H_1,u_L_2,u_l_inf,u_H_1,ux_L_2,ux_l_inf,ux_H_1,uy_L_2,uy_l_inf,uy_H_1,uz_L_2,uz_l_inf,uz_H_1,sigma_L_2,sigma_l_inf,sigma_H_1,sigmaxx_L_2,sigmaxx_l_inf,sigmaxx_H_1,sigmaxy_L_2,sigmaxy_l_inf,sigmaxy_H_1,sigmaxz_L_2,sigmaxz_l_inf,sigmaxz_H_1,sigmayy_L_2,sigmayy_l_inf,sigmayy_H_1,sigmayz_L_2,sigmayz_l_inf,sigmayz_H_1
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