VelocityControl with relative setpoints

[jveijck]

Currently the VelocityControl has an input wanted position in Field Coordinate System (FCS).
For most use cases this sufficient. In some use cases the user want to move relative (using RCS).

Use case: testing or experiments
A use case is during testing or experimenting on the field.
User want have options to move the robot 1 meter to the right, or rotate 90 degrees. etc.
In that case the user can translate a relative move to FCS based on the current position (in FCS).

Use case: substitute procedure
Another use case can be during the substitute procedure. Then a user can move the replaced robot to location near the team area (possible non-green area). The robot can use self localization to move to a intermediate position near the team area. The move from the intermediate position into the team area can not be performed using FCS (assume self loc is not working properly outside the green field). Therefore a relative move would be useful. For the substitute robot is located in the team area. the robot should move relative to an intermediate position in the green field. On the intermediate position, the self localization becomes valid, and it can continue to its desired position on the field.

Proposal
Extend inputs for VelocityControl with enum which indicates if wanted position is in FCS or RCS.