Running head orientation in human aware navigation

If the head_orientation node is running, calculation of head angles will be turned on during human_aware_navigation and turned off after completion or preemption. If head_orientation is not running the service calls will fail but this does not influence the behaviour of human_aware_navigation. The actual orientation is currently not used during navigation but running can be utilised for visualisation and data generation.

Additionally, this PR adds an action server that was used during the review. This just encapsulates the normal idle behaviour but also starts and stops the head_orientation calculation for visualisation.

This was running during the review and should therefore be tested enough.