Refactor YarpRobotControl::setReferences function to include optional current joint values and avoid to switch control mode in YarpRobotControl::setReferences

[GiulioRomualdi]

This pull request restructures YarpRobotControl in the following manner:

• It avoids automatically switching the control mode when a reference is set via YarpRobotControl::setReferences. Refer to issue #820 for more details.
• Furthermore, setReference can now accept a vector of joints as input (optional). If provided, YarpRobotControl::setReferences avoids calling getEncoders from the interface to check if the maximum error is lower than the acceptable threshold.

Finally, it updates the utilities to work with the new modifications

[!WARNING]
As previously mentioned in issue #820, upon merging this PR, several existing code instances will stop functioning. Users should update their code by calling YarpRobotControl::setControlMode() with the desired control mode once before entering the main control loop.

[GiulioRomualdi]

cc @mebbaid @isorrentino @S-Dafarra @evelyd @rob-mau @traversaro