Added a defaullt configuration file with all the parameters.

config/default_config.yaml

+# sensor information
+base_frame_id: "ana/base_footprint"
+min_range: 0.1
+max_range: 50.0
+sensor_height: 0.3
+# node configuration
+debug: True
+max_inc: 0.3
+min_inc: 0.05
+inc_area_filter: 10
+max_ring: 10
+# farthest point computation
+farthest_enable: True
+farthest_num_rings: 9
+# virtual point computation
+virtual_enable: False
+virtual_floor_threshold: 0.03