added diagnostics message, dashboard, youbot battery monitor and adjust sim parameter

short summary of our additions/changes:

- added diagnostic messages to youbot_oodl
- added diagnostic aggregator
- added a dashboard
- added dashboard aggregator
- added battery monitor
- increase controller parameters for the gripper in simulation (gripper could not open if there was an object in the gripper).


to test the new functionality you have to start the following files:

- roslaunch youbot_oodl youbot_oodl_driver.launch
- roslaunch youbot_dashboard dashboard_aggregator.launch
- roslaunch youbot_diagnostic_aggregator diagnostic_aggregator.launch
- roslaunch youbot_dashboard youbot_dashboard.launch

For the battery monitor, please read the README in the respective package