Send messages with an array of letters each with an array of strokes

[dhood]

Currently, the trajectory message which is sent to the tablet and the robot to execute is of type nav_msgs/Path. Multiple letters are sent within this message, with the sequence ID in the Point symbolising "pen up" (i.e. if seq==0, line to point will be drawn by tablet, else line will not be drawn). This was done to avoid needing to make a custom message with ROS java (and the concatenating of letters into the message was doing to make the interaction faster by only needing to send one trajectory, with its start time sufficiently in the future to account for transmission delays). The message to write should be sent as an array of letters which each have an array of strokes, rather than in this hackish nav_msgs/Path way. Also, an ACK system should be in place.