LIDAR sensor resolution parameters

[acschang]

The resolution parameters for horizontal scan resolution, vertical scan resolution, and range resolution do not currently have any impact on the simulated LIDAR model. Furthermore, adding in the necessary hooks to set scan resolution correctly will cause issues in the simulation as the logic to handle a scan resolution that is not 1.0 are not present. The reference documentation for how these parameters should function is on the Ignition Robotics docs page.

The addition of the adding hooks to set horizontal and vertical scan resolution can be seen in #83 . This does not contain the ranging resolution adjustment. These functions would need to be used in the constructor for the GPU LIDAR and then the logic to factor in these parameters would need to be included when updating and publishing scan data.