Change FT sensors names for compatibility with icub-models >= 2.0.0, robots-configuration >= 2.5.0 and ergocub-software >= 0.3.4

[traversaro]

Fix robotology/icub-models-generator#242 .

icub-models 2.0.0 changed the name of the FT sensors in the URDF from being named <identifier>_ft_sensor (like l_arm_ft_sensor, l_leg_ft_sensor, ...) to <identifier>_ft (like l_arm_ft, l_leg_ft, ...).
However, the yarprobotinterface configuration files continued to refer to the sensors as <identifier>_ft_sensor, creating errors for software that was trying to match sensors find in URDF and sensors as exposed by the YARP's multipleanalogsensorsserver device.

This PR changes all the instances of iCub configuration files to <identifier>_ft, restoring compatibility with icub-models 2.0.0, robots-configuration releases >= 2.5.0 and ergocub-software >= 0.3.4, see robotology/robots-configuration#562 .

Note that the name of the joint to which the sensor is attached remained <identifier>_ft_sensor, both before and after icub-models 2.0.0 release.

[GiulioRomualdi]

Thank you @traversaro. I will merge with squash