reem_robot: allow for different joint trajectory params in sim

The assumption that joint trajectory controller parameters were the same
in simulation and on a real robot was previously made.
Now that we need them to be different, they need to be loaded from a
robot or simulation-specific launch file.
reem_description: add mimic joint to the unactuated joints of the hand

This is to make moveit ignore them when generating trajectories
Use the gazebo_ros_multicamera plugin for stereo

Re-define urdf for the stereo camera so that libgazebo_ros_multicamera.so plugin is used.
Merge pull request #6 from jordi-pages/update-stereo-urdf

Use the gazebo_ros_multicamera plugin for stereo
Merge pull request #4 from po1/jtc-params

reem_robot: allow for different joint trajectory params in sim
reem_description: make use of 'robot' parameter
Merge pull request #5 from po1/hand-mimic

reem_description: add mimic joint to the unactuated joints of the hand
Merge pull request #8 from po1/use-robot-param

reem_description: make use of 'robot' parameter