Merge pull request #1 from mgriessler/master

SubSim added readme
thruhster_driver: fixed bug with changing to MagneticField message
sub_scripting: initial
sub_launch: added example "square" mission
added Sub.visual_align and mission to test it
sub_launch/sub_scripting: changed Sub.move to allow multiple edits
sub_launch/sub_scripting: sped up visual_align
added recovery object mission
sub_scripting/sub_launch: use tf and dvl range to more generically and quickly align to targets
added a way to see the difference between the trajectory and odometry positions x,y,x. rosrun traj_odom_diff then plot the pose_diff topic