add image reconstruction config file

demo/image_reconstruction_config_file.cfg

+[data]
+data_path = Data/M87_15GHz.ms
+spectral_window = 0
+polarizations = stokesiavg
+
+
+[sky]
+fov_x = 100mas
+fov_y = 50mas
+npix_x = 1024
+npix_y = 512
+offset_mean = 30.0
+offset_std_mean = 1.0
+offset_std_std = 0.1
+fluctuations_mean = 4.0
+fluctuations_std = 1.0
+flexibility_mean = 2.4
+flexibility_std = 0.8
+asperity_mean = 0.4
+asperity_std = 0.4
+loglogavgslope_mean = -4.0
+loglogavgslope_std = 1.0
+
+
+[response]
+do_wgridding = False
+epsilon = 1e-6
+nthreads = 1
+
+
+[optimization]
+iteration_limit_of_AbsDelta = 600
+iteration_limit_of_NewtonCG_1 = 15
+iteration_limit_of_NewtonCG_2 = 20
+n_iterations = 20
+mgvi_samples = 2