Implement automatic calibration system

This patchset makes a number of improvements to turtlebot_calibration to make it nearly automatic:

1.  Retrieve the current calibration parameters from dynamic_reconfigure and use them to calculate the new parameters, no more manual multiplying
2.  Apply the new parameters to the currently running ros instance using dynamic_reconfigure, no more restarting the turtlebot
3.  Add warnings and references about the gyro range parameter, since this seems to be the biggest hangup for new users
4.  Use the Kinect's serial number (or the usb <-> serial adapter's id if no kinect is available) to save the calibration settings in a standard location.  These settings can then be used by a load script during the turtlebot bringup to help take the pain out of dealing with multiple turtlebots. See this pull request for more information: https://github.com/turtlebot/turtlebot_create/pull/14
5.  Fix the scan topic issues for now, closes issue #69

This patchset (and the referenced pull) have allowed me to quickly calibrate all of my turtlebots and copy the resulting configurations to all laptops.  Since it's nearly automatic it could also be used as part of a script, for instance calibrating the robot before doing something else.