add JTA for arm and set-impedance-param

[k-okada]

Added Joint Trajectory Action for arm and service to set impedance params.

• if you find any issues please don't hesitate to let me know.

thanks, here are few comments

• i remember cst0/spot_ros was forked repository from https://github.com/clearpathrobotics/spot_ros, but did you remove this connection recently? why? I also contribute to clearpathrobotics so it is hard for me to manage this situation.
• Do you have any plan to change https://github.com/cst0/spot_ros/blob/cst/spot_arm/spot_msgs/action/OpenDoor.action interface, we need to set the position of door handle in the image programmably, in additino to using GUI.

[k-okada]

added pick_object_in_image using
2c6445b#diff-1f70ae2edf14caaba4d9689adbfd88faf730fe06f97e7af09ecb2f495232d350 message, this is almost equivalent to grasp_point_userinput service, but pass target position via ActionLib instead of GUI.

see jsk-ros-pkg/jsk_robot@37b4900 for example