Handle TCP Offset for FR3 in RCS

[juelg]

How franka intents to handle the TCP offset is through the desk interface as shown below.

However, to unify the TCP configuration between simulation and hardware, the offset should only be handled by RCS and franka should always return the flange position.

• FR3 needs to be configured to return the flange position in desk. This should be into the documentation (@khaledmohamed00 ) and we can implement a check in move_home to verify that the TCP is correctly configured
• get_cartesian_position in FR3.cpp must be adapted to apply cfg.tcp_offset before returning the value
• set_cartesian_position_internal as well as osc_set_cartesian_position must remove the configured offset before handing down to libfranka.

[juelg]

Implemented in #205