add forward_chain_command_controllers

This PR introduces a new template class **forward_chain_command_controller**, with which it is possible to send commands to a kinematic chain consisting of several joints. Additionally three new controllers are added which use this class:
- effort_controllers/chain_effort_controllers
- velocity_controllers/chain_velocity_controllers
- position_controllers/chain_position_controllers

The controllers subscribe to a topic "command" of type std_msgs/Float64MultiArray and use the float64[] data field as command values interpreting the values as position, velocity and efffort depending on the control domain respectively.
This statement is redundant, `e.what()` above will output ([source](https://github.com/ros-controls/ros_control/blob/indigo-devel/hardware_interface/include/hardware_interface/internal/resource_manager.h#L109)):
```
Could not find resource 'name' in 'interface_type'.
```
If you want to be specific that the missing resource is a joint, a variant of this statement is implemented [here](https://github.com/ipa-fxm/ros_controllers/blob/indigo-devel/joint_trajectory_controller/include/joint_trajectory_controller/joint_trajectory_controller_impl.h#L299), which yields

```
Could not find joint 'name' in 'interface_type'.
```