Adds Gripper Position Playback to Joint Trajectory File Playback Example

[rethink-kmaroney]

• Adds gripper open/close to recorder through cuff button interaction
• Adds gripper position playback to joint_trajectory file_playback example

[rethink-rlinsalata]

Looks pretty good, wonder if we need to worry about the deadband at all.

[rethink-kmaroney]

When you create the new gripper instance the default parameters will be set. The deadband is typically below the noticeable commanded here.