ergoCub SN001/ ergoCubGazeboV1_1*: the waist imu is still added as xml blob to the urdf

[Nicogene]

Task description

This is not a problem, but I noticed that the waist imu is added as xml blob, because when we didn't have creo2urdf we made some workarounds:

• Workarounds, limitations/missing features in ergocub 1.0 urdf #106

ergocub-software/urdf/creo2urdf/data/ergocub1_1/ERGOCUB_all_options.yaml

Lines 1054 to 1085 in d6eba99

	# imu waist (workaround since simmechanics was not updated)
	- |
	<link name="waist_imu_0"/>
	- |
	<joint name="waist_imu_0_fixed_joint" type="fixed">
	<origin xyz="0.0354497 0.00639688 0.060600" rpy="1.5708 0 -1.5708"/>
	<parent link="torso_1"/>
	<child link="waist_imu_0"/>
	<dynamics damping="0.1"/>
	</joint>
	- |
	<gazebo>
	<plugin name="ergocub_yarp_gazebo_plugin_IMU" filename="libgazebo_yarp_imu.so">
	<yarpConfigurationFile>model://ergoCub/conf/gazebo_ergocub_waist_inertial.ini</yarpConfigurationFile>
	</plugin>
	</gazebo>
	- |
	<gazebo reference="torso_1">
	<sensor name="waist_imu_0" type="imu">
	<always_on>1</always_on>
	<update_rate>100</update_rate>
	<pose>0.0354497 0.00639688 0.060600 1.5708 0 -1.5708</pose>
	<plugin name="ergocub_yarp_gazebo_plugin_IMU" filename="libgazebo_yarp_imu.so">
	<yarpConfigurationFile>model://ergoCub/conf/gazebo_ergocub_waist_inertial.ini</yarpConfigurationFile>
	</plugin>
	</sensor>
	</gazebo>
	- |
	<sensor name="waist_imu_0" type="accelerometer">
	<parent link="torso_1"/>
	<origin rpy="1.5708 0 -1.5708" xyz="0.0354497 0.00639688 0.060600"/>
	</sensor>

But I don't see the waist imu csys in the simulation model cad.

Definition of Done

We export the waist imu as sensor not as xmlBlob

cc @Mick3Lozzo @pattacini