Added utility functions for ensurance of pose transformation

These functions were formerly part of cram_moveit, but turned out to be non-moveit-specific. As they are used in other packages, they are moved to cl-tf2 to not introduce unnecessary dependencies towards cram_bridge (which contains cram_moveit).
How about a dependency on `cl-tf`? In order to make the utility functions *really* useful and simple to call, it would be great if they could consume parameters of type `cl-tf:posestamped`, and process them accordingly. Or is there a conceptual drawback on that?