FK solvers query should allow to spec which coordinates to use

[mfrigerio17]

For any desired output pose of T relative to R, the pose can be expressed with coordinates of any frame F.
It is just common practice (as well as a consistently overlooked implicit constraint) to have F equal to R - that shall be the default when no F is specified.

At the moment there is no way to mention F in the query.

For example, I may want to know the position of the end effector relative to some intermediate link in the kinematic tree, but with base-frame coordinates