Adds 'use_collision_mesh' arg to the robot description

[rickstaa]

This commits gives users the ability to load the robot_description urdf with the collision meshes instead of the collision geometries. This is for example useful if people want to use less strict Mesh-based collision properties for third party planners in their packages.

For the moveit_tutorials for example, the movement with the geometry messes is to course (see moveit/panda_moveit_config#72 (comment)). In that case, or the geometries need to be improved or we might want to use the meshes instead.

[rickstaa]

I can of course also change the name of the variable to, for example, strict_collisions.

[rhaschke]

👍 As a user, I definitely want to have an option to resort to these fine-grained meshes.
Is there an option to disable the internal self-collision checking of the robot controller (and only rely on planning methods)?

[rickstaa]

@rhaschke Do we want to keep this open? It is related to #189 but not fully similar since for the arm still geometries are used. I think #189 is good enough for the panda_moveit_config and my own experiments.

[rhaschke]

As Franka pointed out that the internal self-collision checking cannot be disabled or changed by any means, it doesn't make sense to plan with the detailed meshes. However, for environmental collisions, the same problem arises as for the hand: While planning might fail with the coarse self-collision models, the robot might perfectly fit into a narrow passage with the detailed meshes.
Thus, actually, #189 should be extended to apply the same idea to the whole arm, i.e. define detailed meshes for environmental collisions and use separate coarse models for the self-collision. Instead of the name coarse, we should use another suffix, e.g. sc to indicate their use for self-collision checking.

I think, this PR here, can be closed.

[rickstaa]

Makes sense. Do you want to extend #189 or create a separate pull request?

[rhaschke]

See #199 😉