Updated description for lwa4p

[destogl]

Hi all,

trying to create inverse kinematics for lwa4p we found out that the meshes are wrong and coordinate systems not exactly as defined by Schunk. In that way transformations between links are simpler, rotating around only one axis (easier debugging).
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So we created new description (it is compatible with the old one) and we added correct and more detailed meshes and updated Schunk/Blue color so that the robots looks nicer now.

Also an additional tool_link is added to enable more user-friendly attaching of tool descriptions to the robot.

[ipa-nhg]

There are some nice features within this PR but some of the changes break our convention. We've actively decided to not use the Schunk convention but use the ROS convention for coordinate systems (which is always rotate arount the z-axis and z-axis pointing from root/body to tool/finger). We'd like to stick to the existing convention.

Also please consider the following:

• do not use scaling in the urdf (instead: scale your model)
• do not use origin offsets in the geometry and collission tags (instead: move the origin in the model)
• use highly detailed models only for geometry tag and use simplified models for collision tag (to speed up collision checking)
• axis of joint should always be <0, 0, 1>

[destogl]

@ipa-nhg: Thanks for your comments. I will check all the points you mentioned so I will create here short ToDo list:

• scale models
• move origins of the models
• generate simplified models for collision checking
• objects should always rotate around <0, 0, 1> as this is a ROS convention

[destogl]

@ipa-nhg: just for info: this will take some time, since it is time consuming but does not directly bring any value...