adding joystick_follower demo application

[tfoote]

A neat demo we've been running integrating joystick control of the follower app for enabling/disabling and remote control.

Looking at this PR we should probably rename the package. Any other thoughts. I will also want to improve the documentation, but I'm opening the PR for higher visibility.

[stonier]

Alot of duplication in there I'd not like to maintain.

I'd be tempted to just insert the joystick scripts/configuration into the follower launcher (or follower rapp launcher) as its a nice feature to have regardless. Then you can just start the regular minimal with the rapp_auto_start arg for turtlebot_rapps/follower.

[tfoote]

Indeed the only extra dependency brought in by making the follower depend on the teleop is the joy package. See below for the diff. The other packages needed directly are already in the dependency tree. See below for the diff.

I'll reformulate this to be an argument to the follower launch.

tfoote@yeti:~/work/turtlebot/turtlebot_apps Last: [1] (0s Seconds)
$ rospack depends turtlebot_teleop | sort > /tmp/teleop_depends
tfoote@yeti:~/work/turtlebot/turtlebot_apps Last: [0] (1s Seconds)
$ rospack depends turtlebot_follower | sort > /tmp/follower_depends
tfoote@yeti:~/work/turtlebot/turtlebot_apps Last: [0] (0s Seconds)
$ diff -u /tmp/teleop_depends /tmp/follower_depends 
--- /tmp/teleop_depends 2016-03-09 14:52:34.157953228 -0800
+++ /tmp/follower_depends   2016-03-09 14:52:43.489905948 -0800
@@ -58,7 +58,6 @@
 image_geometry
 image_proc
 image_transport
-joy
 kdl_conversions
 kdl_parser
 kobuki_auto_docking
@@ -81,9 +80,13 @@
 message_runtime
 nav_msgs
 nodelet
+nodelet_topic_tools
 openni2_camera
 openni2_launch
 orocos_kdl
+pcl_conversions
+pcl_msgs
+pcl_ros
 pluginlib
 python_orocos_kdl
 rgbd_launch
@@ -157,10 +160,12 @@
 turtlebot_bringup
 turtlebot_capabilities
 turtlebot_description
+turtlebot_msgs
 unique_id
 urdf
 urdf_parser_plugin
 uuid_msgs
+visualization_msgs
 xacro
 xmlrpcpp
 yocs_cmd_vel_mux