Add fully extended pose: 'extended'

[henningkayser]

This adds a simple named pose 'home' where the group panda_arm_hand is fully extended.

[rhaschke]

I guess you need this pose for the tutorials.
In general, I would argue that named poses (particularly home) are highly subjective to a specific user and task.

[henningkayser]

@rhaschke I agree, how about "extended""?

[rhaschke]

@henningkayser, could you please extend the main comment to argue why you want to add this pose?
This will help in future to understand its need.

[fwalch]

This pose violates the joint limits in joint 4. This is in the URDF, so I'm surprised this isn't flagged by MoveIt.