Gazebo support + urdf model corrections

[L-eonor]

Robotiq85:

• base link visual mesh (robotiq_arg2f_base_link)-> added from Robotiq 140
• gazebo support: mimic joints
• inertial properties
• corrected joint's limits
• hardware interface: EffortJointInterface

Robotiq140:

• gazebo support: mimic joints
• corrected joint's limits
• hardware interface: EffortJointInterface

Related issues:

• solves gazebo simulation: 161
• robotiq 85 model 111
  (Tested in ros-melodic. Relates to this issue: 163 )

(Based on https://github.com/Danfoa/robotiq_2finger_grippers)