Add loosely-typed API to construct roslaunch commands

[tejashah88]

Hello again,

I noticed there's been some activity on the repo and I wanted to add a minor QOL PR to how launch commands are constructed. I didn't like the idea of string concatenating complex arguments so I created construct_roslaunch_command, which is a simple command to take the ROS module, launch file and launch commands and create the launch command string.

The easiest comparision is shown below in robo_gym/envs/ur/ur_avoidance_basic.py:

Before

cmd = "roslaunch ur_robot_server ur_robot_server.launch \
        world_name:=tabletop_sphere50.world \
        reference_frame:=base_link \
        max_velocity_scale_factor:=0.2 \
        action_cycle_rate:=20 \
        rviz_gui:=false \
        gazebo_gui:=true \
        objects_controller:=true \
        rs_mode:=1moving2points \
        n_objects:=1.0 \
        object_0_model_name:=sphere50 \
        object_0_frame:=target"

After

cmd = cmd_utils.construct_roslaunch_command(
    module='ur_robot_server',
    launch_file='ur_robot_server.launch',
    launch_args={
        'world_name': 'tabletop_sphere50.world',
        'reference_frame': 'base_link',
        'max_velocity_scale_factor': 0.2,
        'action_cycle_rate': 20,
        'rviz_gui': False,
        'gazebo_gui': True,
        'objects_controller': True,
        'rs_mode': '1moving2points',
        'n_objects': 1.0,
        'object_0_model_name': 'sphere50',
        'object_0_frame': 'target',
        'ur_model': ur_model
    }
)

I haven't checked if this PR works cleanly with the new changes but you can use the test file as a starting reference. Let me know your feedback on this!

Tejas

[tejashah88]

I fixed the merge conflicts to match the new format