First draft of sensor interfaces.

- Force/torque (wrench)
- Orientation
- IMU (very crude approximation)
Add sensor reference frame field.
Add sensor ref frame field and capability queries.
Merge branch 'master' into sensor_interfaces
Scrape orientation interface prototype.
Explicitly initialize IMU sensor handle members.
Remove Eigen dependency from hardware_interface.

- Expose force-torque and IMU sensor data as const pointers to the raw data.

- Client code should wrap raw data however they prefer.
Merge branch 'master' into sensor_interfaces
Merge branch 'master' into sensor_interfaces
Merge branch 'master' into sensor_interfaces
Update sensor interfaces implementation.

- Use resource managing classes introduced in recent hardware interface rework.

- Conform to unified public API.
Merge branch 'master' into sensor_interfaces
Add missing brace.
Merge branch 'master' into sensor_interfaces
Merge branch 'master' of github.com:willowgarage/ros_control
User error checking
Merge branch 'master' of github.com:willowgarage/ros_control
Make specific transmission interfaces proper types.

- Proper types instead of namespaces allow to provide less cryptic feedback.
  * Using typedefs:
  "transmission_interface::TransmissionInterface<transmission_interface::ActuatorToJointPositionHandle>"

  * Using a new type:
  "transmission_interface::ActuatorToJointPositionInterface"

- Added error message printing to tests for manual inspection.
Revert "Fixed PLUGINLIB_DECLARE_CLASS deprecated errors"

This reverts commit cd9aba265a380bafebb70d63081405d857e9380d.
Merge branch 'fuerte_backport' into sensor_interfaces